Seishun Academy (|青春学園|Seishun Gakuen), or Seigaku (|青学) for short, is the school that the main character, Echizen Ryoma, goes to. It is famous for its tennis club, and was the alma mater of Japan's most famous tennis player, Echizen Nanjirō, the father of the protagonist (who chose to enroll his son in the school for this very reason). The school is in Tokyo (aka Tokyo Metropolis).
Seigaku is one of the few schools shown to have a high school division and a university division. 
- Established: 1925
- Headmaster: Ishikawa Hiroyuki
- Student Body: 1442 (731 boys, 711 girls)
- Coach: Ryūzaki Sumire
- Captain: Tezuka Kunimitsu
- Vice-Captain: Oishi Shūichirō
- Treasurer: Nishi Hideto
- Goods Manager: Kuwahara Naoya
- Tennis Club Membership: 33
In the The Prince of Tennis universe, Seigaku's tennis club was not always the feared monster that it is seen in the run of the series, and was average talent-wise when the school opened in 1925. The appearance of a young Echizen Nanjirō, father of Echizen Ryoma, was what had initially transitioned the club's performance from mediocre into one of the strongest teams in the area.
Although Seigaku was well known for their tennis skills in the past, the absence of Echizen Nanjirō threw the team into somewhat of a slump, leaving them unable to make it to Nationals over the next several years until a first year, Tezuka Kunimitsu, joined the Regulars. His outstanding talents played an important role in starting up where Nanjiro had left off.
With the help of his then-captain Yamato Yūdai, Tezuka became the team's captain and pillar of support at the beginning of his third year. By this time, a few other extremely talented players began making their way onto the team. Yet, despite the obvious talent and potential that Seigaku's tennis club held, a few of the players lacked the heart that it took to win the game (Fuji Shūsuke), while others were simply unaware of their own inner drive toward perfecting their skills (Inui Sadaharu) and bringing their hidden talents to the surface (Kaidō Kaoru).
The arrival of twelve year old tennis genius Echizen Ryoma is what finally lit Seigaku's motivational fuse, allowing them to advance. Feeling inspired, rather than resentment toward the freshman's skills, the team combines intense training, perseverance, trust, and teamwork in order to secure a spot at the Nationals. Stated during the Yamabuki arc, one of Seigaku's flaws is that they do not have a steady doubles team besides the Kikumaru/Oishi Pair; their individual talents are so strong that they do not work well together. In the beginning of the series, Doubles 2 is usually played by the Kawamura/Fuji pair, while later in the series, Momoshiro/Kaido pair and Inui/Kaido pair have taken its place, showing that Seigaku is overcoming its lack of skilled doubles teams. The team is really close with rival schools Fudomine and Rokkaku Middle Schools, and share a strong rivalry with Hyotei Academy.
The team's uniform is blue and white shirts, white shorts (started out as gray for the first nine episodes of the anime, but Echizen is the only member of the team to wear his usual black shorts), and blue and white jackets with the Seigaku logo on the back with several red stripes on the cuffs and collar. The regulars also get their name personally stitched into the jacket. They also have blue warm-up pants with "Seigaku" printed on one side, and usually remove them before a match (Kaido and Echizen are the only ones who never wear these).
By the end of the original series, Seigaku manages to pull off its first National victory after defeating the reigning champions Rikkai Daigaku Fuzoku 3-2.
After the Nationals, Seigaku becomes one of the first Middle School tennis teams having their regulars invited to the U-17 Training Camp, which was only open to High Schoolers prior to their invitation.
Tennis Team Members
Ryūzaki Sumire (竜崎スミレ, Ryūzaki Sumire?)
- Position: Coach, Math Teacher
- Signature Technique: Continuous Ball Pretense (Hora Hora Attack)
Ryuzaki Sumire is the coach of Seigaku's tennis club, as well as one of the school's math teachers. It was thanks to her that Echizen Nanjiro was able to develop his skills. She is the grandmother of Sakuno. She also has a sort-of rivalry with her ex-mentor, Banda Mikiya a.k.a. Banji, who is the coach for Yamabuki. She is always there to yell, but is also considered to be a great and reliable coach. She has a good relationship with her regulars, and participates in their recreational group activities: the bowling reunion and the beach-volley mini-tournament with Rokkaku Middle School.
For the Prince of Tennis live action movie, Ryuzaki's whole personality and back story was changed. Instead of being a middle-aged teacher and ex-coach to Nanjiro Echizen, she is a young, and more cheerful woman as well as Nanjiro's former classmate, who was her reason for playing tennis and becoming coach. She was played by the popular singer Hitomi Shimatani.
Echizen Nanjirō (越前南次郎, Echizen Nanjirō)
- Former Position: Regular, Captain (?)
- Years since Graduation: 25 years ago from the start of the series
Nanjiro is Ryoma's father, and was known as Samurai Nanjiro due to his invincible tennis skills during his professional career. His specialties included the "Nanjiro Zone," which is the completed version of the current captain Tezuka's Tezuka Zone, as well as discovering ambidextry that he calls "Nitoryu" by himself.
- Yamato Yūdai (大和祐大, Yamato Yūdai)
- Former Position: Captain
- Years since Graduation: 2 years ago from the start of the series
Yamato Yūdai is the captain during Tezuka's freshman year. He talks Tezuka into staying in the tennis club as Seigaku's pillar of support, calming him down when he was on the verge of quitting after being injured. Eccentric, insightful and gentle, Yamato has a unique "way" of explaining things that even Sumire Ryuzaki has trouble understanding him. He continued to help the tennis club after he graduated; in the anime, coach Ryuzaki asks him for his guidance when they go to a training camp to prepare for the Kantō conference final against Rikkai Daigaku. In the anime, he comes back as a member of the 3rd Court at the U-17 camp and ends up playing a match against Tezuka, eventually losing to him as Tezuka heads to leave the camp to return to Germany.
- Position: Regular (Captain)
The current captain of the Seigaku tennis team. He is a stern but highly-respected leader. As a player, Tezuka is widely recognised as one of the best singles players and a "National level" player. Tezuka mostly plays singles though he once he played doubles with Inui against Shintenhoji during Nationals.
- Position: Regular (Vice-Captain)
Vice-captain of Seigaku and close friend of Tezuka. Oishi specialises in doubles, pairing with Kikumaru to form the "Golden Pair", being the only middle schoolers to achieve Synchro in the original Prince of Tennis. He plays singles at school against other teammates during ranking matches, but never in actual tournaments. During the Senbatsu Training Camp (anime only), he played a doubles game with Shishido from Hyotei against Kikumaru and Shishido's doubles partner, Ōtori . In New Prince of Tennis, at the beginning of the U-17 Camp, Oishi was forced to play a singles game against partner Eiji. He has also played doubles with Rikkai's Niō.
- Position: Regular
A calm and cheerful player, known widely as a tennis prodigy and Seigaku's No.2. Fuji usually plays singles, though he will sometimes play doubles with Kawamura or Kikumaru (with the latter they form the "Dream Pair"). Apart from his tennis skills, Fuji also possesses unique tastebuds: he enjoys wasabi sushi and Inui's juice. Fuji is also considered sadistic by some fans because he sometimes likes to play tricks on people (and because he once stated that although he likes Inui's juice, he prefers to see other people suffering drinking it). He ususally has his eyes closed and wears a smile unless he becomes serious about something. Never angered on his own behalf, Fuji is highly protective of his friends and younger brother Yuta, and the times he opens his eyes are usually associated with such incidents. Fuji has numerous amazing "counters", which are also useable in other sports, as shown for example in the Prince of Volleyball episode( It's an OVA).
- Position: Regular
A highly agile and flexible player. Specialises in doubles, forming Seigaku's "Golden Pair" with Oishi as well as playing with other team members like Momoshiro and Fuji on occasion. He played doubles once with Ryoma, when he got in a fight with Oishi. He is also shown to be fairly skillful at singles, playing against Higa Chuu's Kai in the Nationals arc for example, and successfully playing against partner Oishi at the U-17 Camp. Nonetheless, Eiji has mentioned that he prefers playing Doubles, finding Singles "too lonely", and remains primarily a Doubles Player. He has also played doubles with Hyotei's Ōtori and Oshitari (Senbatsu Arc). With Oishi, he is among the few middle schoolers to have achieved Synchro .
- Position: Regular
A skilled singles player who plays with pure power, he occasionally plays doubles with Fuji or Momoshiro. Aiming to be Japan's No. 1 "Power Player". Normally meek and shy, his personality changes dramatically when he holds a racket, going into burning mode. The son of a sushi chef, he usually treats his team members to unlimited sushi at his family restaurant as a reward for winning (if they lose they have to eat wasabi sushi, which they all hate, except Fuji).
- Position: Regular
A highly intelligent player, Inui is known for gathering data about the team and their opponents, and takes charge of the team's training. He is skilled at both doubles and singles. A doubles champion in elementary school with close friend Yanagi , he focuses on singles in his first two years of Middle School, and was Seigaku's No.3 before Echizen's arrival. Inui now primarily plays doubles with Kaido, though he played Singles 3 against his old partner Yanagi during the Kanto tournament and with Tezuka during the Nationals semi-finals. Apart from collecting data on everyone, Inui also enjoys creating a series of supposedly beneficial (but increasingly vile-looking) health drinks and using them to motivate the team to train harder. These drinks strike fear in all characters in the Prince of Tennis universe (other teams have also experienced them, as seen for example in the Prince of Barbecue episode).
- Position: Regular (Vice-Captain in the epilogue)
The first 2nd year to be briefly shown and the third 2nd year to be fully introduced, he is known as the Seigaku's number one rascal. His specialties include the Dunk Smash and power moves, as well as faking out the opponents in doubles. He plays doubles with Eiji,Taka, Kaido, and on a rare occasion, Ryoma (though both swore never to repeat that experience). He's good at both doubles and singles. He,Eiji, and Oishi form the "Golden Trio", referring to the occasion he substituted for the injured Oishi to play a successful doubles game with Eiji.
- Position: Regular (Captain in the epilogue)
Another 2nd year, he is originally known as playing singles, but on occasion, he plays doubles with Momoshiro or Inui. Notable moves include the Snake Shot and the Boomerang Snake. He has a devil mode, which has only been shown once when he, and Inui were going against Yanagi and Kirihara in the Nationals. Despite his scary appearance, he has a large soft-spot for animals, showing his kind nature.
Arai Masashi (荒井将史, Arai Masashi)
- Position: Team Member, Strongest Reserve Player (Anime Only)
Masashi Arai is a second year student, and the best reserve player on the team, who is the closest to becoming a regular, almost getting a shot to play in Kantō Tournament finals in the anime when Momoshiro and Kaido were nowhere to be seen. He is known for his hotheadedness and hazing of weaker players. He is as hard on himself as he is on the others during training. In the anime, he also tried to con the Freshmen Trio out of their money. He is also later attacked in another episode by Yamabuki's Jin Akutsu. Although he had a very bitter relationship with Ryoma at first, he cheered him on during his match with Akutsu. He often hangs around with Ikeda and Hayashi.
- Position: Team Member
The first 2nd year to be introduced in the series, he tried to con the Freshmen Trio out of their money by disguising the price of a game, but Ryoma was able to see through the scheme.
- Position: Team Member
The second 2nd year to be introduced in the series, along with Hayashi, he tried to con the Freshmen Trio out of their money by disguising the price of a game, but Ryoma was able to see through the scheme. Possibly because of this, Ryoma holds a slight grudge against Ikeda, completely crushing him during the Second Intraschool Ranking Match, even using his Twist Serve.
- Yoshimura Shun
- Yoshimura Yuu
- Fushimi Ayata
- Hiratsuka Kazuya
- Nagayama Michio
- Nakahama Yuuya
- Ninose Manabu
- Saeki Norifumi
- Tsuda Shuushi
- Sakai (Seigaku)
- Nagayama (Seigaku)
- Kaneko (Seigaku)
- Kishino (Seigaku)
- Position: Regular
The main character in the story, he is the only freshman regular on the Seigaku Tennis team. His specialties include the Twist Serve and several drive volleys. He can also copy other moves from others that he's played. He also knows how to use all 3 of the Pinnacles., though he only activated Pinnacle of Perfection by accident and has yet to master it.
- Position: Team Member (freshman)
He is one of the freshmen trio and is famous for boasting about his 2 years of experience in tennis. He's usually clumsy, but is smart when it comes to describing things from tennis. He and Tomoka don't like each other and usually argue in school.
- Position: Team Member (freshman)
He is one of the freshman trio. His dad is a coach at a large tennis club. Like Katsuo he's usually calm.
Mizuno Katsuo (freshman)
- Position: Team Member (freshman)
He is one of the freshman trio. He is the closest to look like Oishi, however most would assume that he looks more like Kentaro from Rokkaku. He's usually calm. In the anime he is shown to know how to cook.
Note: There are approximately six or more other first years according to the manga's Hyoutei Arc.
Sakuno Ryūzaki: Coach Ryuzaki's grandaughter and a member of the Girls' Tennis Team, she cheers Ryoma & the others with Tomoka.
Tomoka Osakada: She is a student at the school and as she calls herself the head of Ryoma's fan club.
Principal Ishikawa: He is the principal of the School and is shown once before the Kantō region finals.
Like most middle, the boys at Seishun Academy wear a black gakuran, which is a black military like jacket, black trousers, and a white shirt underneath. The uniform is consistent in both the anime and manga.
In the anime, it appears that the color of the Physical Education uniform rotates through red, green, and blue. The color that the students wear in their first year follows them until their graduation, which would then be given to the next year's first years.
Example: If say this year's graduating third years wear the green uniform, the following year's first years will also wear green. These new first years will then only wear the green uniform for the remainder of their junior high school years.
In the boys' tennis club, first years wear their physical education uniform. Only second years wear the blue practice jersey, and only third years wear the green practice jersey (though this may only be Inui as all 3rd year members seen are regulars). Only regular members wear the red, white, and blue jersey and polo shirts. In the anime on the regulars' polo shirt the Yonex symbol was added right above the school's name on the left breast.
Unlike the boys', the girls' uniform is a completely different color scheme in both the anime and manga. The manga version of the uniform (to the right) is made up of dark blue checkered skirt, a lighter blue sailor jacket that is gold/yellow trimmed, a white blouse, and a red bow.In the anime, the uniform is similar in style, but the blue is replaced with different shades of green. The gold trimming is changed to a dark green to match the new color of the skirt, and the red bow is changed to pink. The anime version of the uniform also consists of knee high black socks and brown loafers.
The girls' uniform is somewhat different in style and majorly different in color as compared to its male counterpart.
While the boys have a multi-color and striped collar, the girls have a clean white one. Both the sides and the sleeves of the shirt are gold yellow with blue lines on the borders and going down the sleeves instead of the boys' solid blue sides and sleeves with white stripes. The girls also wear a gold yellow skirt/skort (shorts made to look like a skirt) in place of the boys' white shorts.
Other Known Clubs
- Sumo Wrestling
- Ping Pong
- Tennis—Girls' Division
- Out of all the schools, Seishun Academy is the only tennis club which has its member dressed in different uniforms for each grade level. Other schools' tennis clubs have all of their members dressed in the same polo shirts and jersey/jacket for all grades.
- Seigaku is not close to the Kanagawa prefecture since Ryoma had to run 23.8 km (14.8 mi) to get his rackets restrung before coming across Akaya from Rikkaidai.