Jan Vacek (yahn VAH-tseck; born 10 May 1976) is a retired professional male tennis player from the Czech Republic.

Vacek reached a career high ATP singles ranking of World No.

He also reached a career high ATP doubles ranking of World No.

Vacek successfully played in all four Grand Slam tournament main draws, highlighted by reaching the fourth round at the 2002 Wimbledon Championships.

Unseeded at the 2001 Brasil Open, he won the singles championship, defeating eighth seed Mariano Zabaleta 3–6, 6–4, 7–6(8–6) in the second round, sixth seed Alexandre Simoni 7–6(7–5), 6–2 in the semi-finals and fifth seed Fernando Meligeni 2–6, 7–6(7–2), 6–3 in the final to claim his first and only ATP Tour title.