Jonáš Forejtek (born 10 March 2001) is a Czech professional tennis player.
He has achieved a career-high ATP ranking of 565 in singles and 364 in doubles.
He also has reached a career-high ITF juniors ranking of 12 in the world.
On 25 January 2019, Forejtek and his partner Dalibor Svrcina won the 2019 Australian boys' doubles title, beating Emilio Nava and Cannon Kingsley in the finals.
In the 2019 US Open boys’ singles Forejtek defeated Emilio Nava in the Final 6–7(4), 6–0,6–2.