Jan Jacobus ("Sonny") Silooy (born 31 August 1963 in Rotterdam, Zuid-Holland) is a former Dutch footballer, who is now an assistant manager for Major League Soccer club D.C. United.
Silooy played as a right or central defender and is one of the legends of Ajax Amsterdam, where he made his debut on May 3, 1981, playing over 250 league games for the Amsterdam club in two separate periods. Silooy also played for Matra Racing, Arminia Bielefeld, De Graafschap and the amateurs of GVV Unitas from Gorinchem. He played in the 1996 UEFA Champions League Final against Juventus, but missed a key penalty in the shootout which Ajax ultimately lost.
Silooy obtained 25 caps for the Netherlands national football team, including 8 appearances in Euro 88 qualifying, but never played in a major international competition.
Silooy was also coach of the Jong Ajax youth academy and juniors team. In 2010 he was appointed as headcoach of new branch Dayton Dutch Lions.
He left Dayton Dutch Lions to become an assistant coach with the Major League Soccer club D.C. United.
- Eredivisie: 1981–82, 1982–83, 1984–85, 1989–90, 1993–94, 1995–96
- KNVB Cup: 1982–83, 1985–86, 1986–87, 1995–96
- Johan Cruijff Shield: 1993, 1994, 1995
- European Cup Winners' Cup: 1986–87
- UEFA Cup: 1991–92
- Intercontinental Cup: 1995
- UEFA Super Cup: 1995