is an Australian former association football player and he is the currently head coach of Chinese Super League club Shanghai Port. As a player, he played as a defender, and represented the Australia national team at international level winning 46 caps and scoring 10 goals between 1994 and 2006.

After beginning his professional career in the Australian National Soccer League with Sunshine George Cross in 1989, Muscat played eight seasons in the United Kingdom with Crystal Palace, Wolverhampton Wanderers, Rangers and Millwall. He returned to Australia in 2005 for the first time since leaving South Melbourne in 1996 to captain Melbourne Victory in the inaugural season of the A-league. His playing style was brutal defence with little regard for accumulating yellow cards or avoiding injury to opponents, a reputation that was so strong that while at Rangers he was never picked for an Old Firm derby due to the perceived risk that his explosive temper causing a major incident or costing Rangers the match by being sent off. He ended his A-League career in disgrace after deliberately injuring Adrian Zahra with a disgraceful tackle that was widely describe as an assault by the football media.

Muscat retired from professional football in March 2011 after Melbourne Victory's 2011 AFC Champions League campaign, citing his growing frustration at his inability to keep pace with the game. Muscat briefly rejoined his former club Sunshine George Cross for part of the 2011 Victorian State League Division 1 season.

During his international career, Muscat represented the Australia U-20 side at the 1991 FIFA World Youth Championship in Portugal and the 1993 FIFA World Youth Championship in Australia. He represented the Australia U-23 side at the 1996 Summer Olympics. After making his full international debut for Australia in September 1994 against Kuwait, Muscat represented the national side at the 1997 FIFA Confederations Cup, 2000 OFC Nations Cup, 2001 FIFA Confederations Cup and the 2005 FIFA Confederations Cup.

After several seasons as an assistant coach, Muscat was appointed head coach at Melbourne Victory in October 2013. He has coached Victory to the 2014–15 A-League Premiership, the 2014–15 A-League Championship and success in the 2015 FFA Cup. He left the role in 2019.

Muscat is Melbourne Victory's all time top scoring defender, with 35 goals in all competitions.