Jacob "Sjaak" Troost (born 28 August 1959) is a Dutch retired footballer who played as a defender.

Born in Pernis, South Holland, Troost played his entire career with local Feyenoord, making his Eredivisie debut on 9 April 1978 in a 0–1 away loss against FC Volendam and becoming an undisputed starter from the 1981–82 season onwards.

He appeared in 29 games in 1983–84 as the Rotterdam club won the league after a 10-year wait, scoring once in a 4–0 win at Fortuna Sittard as the campaign also ended with Dutch Cup conquest.

Troost appeared in 397 official matches for Feyenoord, retiring in June 1992 at nearly 33.

His debut came on 9 September 1987 in a 0–0 friendly with Belgium, in front of a familiar crowd at De Kuip (90 minutes played).