Kunimitsu Tezuka (Japanese: 手塚 国光, Hepburn: Tezuka Kunimitsu) is a fictional character in the manga and anime series The Prince of Tennis. He was created by Takeshi Konomi, who described Tezuka as the character with whom he has the least in common. Tezuka's character is well received by readers and has ranked among the top five most popular characters in every Shonen Jump character popularity poll of the series. He is known for his seriousness, strictness, and fair leadership as the captain of the team. Tezuka often sacrifices his injured left arm to defeat opponents and lead his team to victory.

In the story, he is introduced as the strict and serious captain of Seishun Academy's ("Seigaku" for short) tennis team who enforces order within his team, often forcing its members to run laps. With his all-around tennis style and advanced techniques, Tezuka is considered to be a national-level tennis player by many of the other characters.

Tezuka encourages the series protagonist, Ryoma Echizen, to develop his own style of tennis, leading the latter to consider him as both a mentor and rival. Throughout the series, Tezuka continues to struggle with consistent pain in his left arm, which was inflicted on him two years prior to the main storyline by an upperclassman. However, he often sacrifices the use of his arm to defeat opponents and lead his team to the National Tennis Tournament. In addition to appearing in the series other media, including musicals, films, and soundtracks, different types of merchandise have been released in his likeness, including figurines and jewelry.

Tezuka's character has been well received by readers since his introduction, having ranked in the top five most popular characters in every Shonen Jump character popularity poll of series. He has also remained in the top 10 annual Valentine Chocolate Recipient rankings that Takeshi Konomi releases in the manga, in which readers mail in who they want to send chocolate. However, in publications on manga and anime, his character has received mixed reviews. Reviewers comment on his lack of originality and that the impossibility of one of his techniques is part of why the story seems unrealistic. Though one reviewer questions his likability as a protagonist, his personality is praised, with one praising his devotion as one of the highlights of the series, and another commenting that he is a good captain who properly motivates the main character.

Parts of Tezuka's history are revealed throughout several flashbacks in the story. Three years prior, when he was still a relatively unknown tennis player, Tezuka easily defeated the Junior Tennis Tournament's runner-up, Genichiro Sanada, and played evenly against the champion, Seiichi Yukimura. Upon his entrance into Seishun Academy nearly a year later, Tezuka was already a better tennis player than most of his upperclassman. However, when his teammates found out that he is left-handed even though he played against them with his right, they viewed him as arrogant, leading to a jealous teammate injuring his left arm. Despite having made a promise to Shuichiro Oishi that he would lead Seigaku to the Nationals, Tezuka decided to quit the tennis club because he did not want to be on the same team with people who used their racquets to hurt others. Nonetheless, his skills were recognized by then-captain Yūdai Yamato, who wanted Tezuka to become Seigaku's "pillar of support", and entrusted him with the dream of going to the Nationals, which convinced Tezuka to stay.

During that same year, Shusuke Fuji defeated Tezuka in a private tennis match, but Fuji was displeased with the outcome after learning about Tezuka's injury, promising to play him again after his arm heals. Over time, Tezuka secured a regular spot on the team despite being a first-year. By his second year, he became the team's vice-captain and defeated Hyotei Academy's captain during a tournament. Despite not being at full strength due to his injury leading to chronic problems, and his sealing of a powerful technique that required the use of his left arm, Tezuka eventually became known as a National-level tennis player. He was invited to an elite tennis training camp, but due to persistent arm pain, he declined the invitation without explanation to the organization.

Tezuka's personality remains consistent throughout the series as he is always serious about everything he does, especially his duties as captain of the tennis team. Despite being very strict, he is fair and sticks to his word, punishing everyone even if the rules are broken by only a few. He would often make the entire team run laps when they break the rules and one of his trademark phrases is ("Yudan sezu ni ikō"). He is determined to lead his team to the Nationals, which often results in him ignoring his doctor's warnings against him playing in arduous tennis matches – considering his health secondary to the team's success, and continuing to risk re-injury in his matches to ensure their victory. Tezuka even risks it all during a match against Ryoma since he sees the boy as the one to succeed him as the team's new "pillar of support".

Also, no matter the situation, he is shown to be rather inexpressive, never changing his stoic expression. However, when he re-injures his arm during his match against Keigo Atobe, he is shown to writhe in pain. This becomes a traumatic memory that makes him unable to lift his arm over his shoulders, fearing the thought of feeling that pain again. He learns to overcome this during his medical retreat in Kyūshū. Due to his experiences, he dislikes those who use tennis to harm others.