Zhang Zhizhen (simplified Chinese: 张之臻; traditional Chinese: 張之臻; pinyin: Zhāng Zhīzhēn; Mandarin pronunciation: [ʈʂáŋ ʈʂɻ̩́ ʈʂə́n]; born 16 October 1996) is a Chinese professional tennis player. He reached a career-high ATP singles ranking of world No. 31 in July 2024 and a doubles ranking of No. 47 in July 2024. As of July 2023, he became the highest-ever ranked Chinese male tennis player. He is the current No. 3 Chinese player. He has won three singles and two doubles titles on the ATP Challenger, and two singles and two doubles titles on the ITF Futures Tour. He won a silver medal in mixed doubles alongside Wang Xinyu at the 2024 Summer Olympics.

In 2021, Zhang became the first Chinese man in the Open Era to play in the main draw at Wimbledon. In October 2022, he became the first Chinese male player to reach the top 100 in the ATP singles rankings. Then, in 2023 in Madrid, he became the first Chinese man to reach an ATP Tour Masters 1000 quarterfinal.

In 1996, Zhang was born to a sports family in Shanghai. His father Zhang Weihua (张卫华) played football in the Chinese Jia-A League as a defender for Shanghai Shenhua. His mother was a member of the Shanghai shooting sports team and later worked at the Shanghai bureau of China Telecom. From age 4 to age 6, he had two weekly swimming classes at kindergarten, and his parents enrolled him to tennis lessons in the weekends. When he reached elementary school, his parents let him decide which one of the two sports to continue. He chose tennis because the swimming teachers were strict, partly because of their responsibility of ensuring swimming safety. From 2008 to 2013, he was coached by Shao Donglu (邵东路).

In December 2015, he fractured a bone in his left foot after stepping into a pit during a sprinting exercise in a park. He underwent surgery two months later, and his form dropped significantly until May 2017. In 2016, Zhang signed with the Croatian tennis agent Ivan Ljubicic. Since then, Zhang's main residence moved to Lošinj Island, Croatia. In June 2022, he graduated with a degree of human resources management from Shanghai Jiao Tong University.

Zhang is married and has one child.

Zhizhen Zhang began his career in Chico, California, playing on the ITF Futures Tour. Despite losing to Jason Jung in straight sets, Zhang rebounded at the Joplin Futures tournament, recording his first win as a professional against Daniel Yoo, before losing in straight sets to unranked American Gonzales Austin. Zhang lost in the first round of the following two futures tournaments he entered. At the 2012 Shanghai Rolex Masters, Zhang – only sixteen at the time – was given a wild card entry into the qualifying draw; he lost to world number sixty one Brian Baker, winning just three games in his debut clash with a top one hundred ATP player.

After a six month hiatus from professional events, Zhang made his 2013 ITF Men's Circuit debut in May at the USA F12 challenger, where Greg Ouellette got the better of the youngster in three sets. Zhang continued to play professional events sporadically, managing to come through qualifying to make the 2013 Shanghai Challenger's main draw – his first ATP Challenger Tour appearance. Zhang would skip half of the 2014 ITF Men's Circuit, finishing the year with only thirteen participations in senior-level events, including a quarterfinal showing at a Futures tournament in Cyprus.

March brought Zhang his first victories of 2015, where he bested Jan Zieliński and top-400 player Bastian Trinker in Turkey's 11th Futures event of the year. Zhang struggled to maintain consistent form in the following months, exiting in the opening two rounds of every tournament he played in, before winning the Mont-de-Marsan Futures tournament in June; this was Zhang's first ITF World Tennis Tour title. French tournaments continued being the bearers of good results for Zhang, as he followed his Futures title with a second final three weeks later, this time in Bourg-en-Bresse.