Joseph "Jef" Planckaert (4 May 1934 – 22 May 2007) was a Belgian racing cyclist. He is seen as one of the best Belgian cyclists of the 1950s and 1960s.
His best season was 1962, when on the citadel of Namen he became Belgian champion, won Paris–Nice and the Tour de Luxembourg, won Liège–Bastogne–Liège and became second in the Tour de France. He also won Omloop Het Volk in 1958, and Four Days of Dunkirk in 1957, 1960 and 1963.
In the Tour de France he finished 6 times in the top 20 in the final standings. In 1961 he won the 6th stage. In 1962, Planckaert wore the yellow jersey for 7 consecutive days. Planckaert ended his career in 1965.