Sam Justin Gallagher (born 5 May 1991) is an Australian footballer who last played as a central defender for Manly United.

[6] His debut with the Victory ended almost as soon as it began; in just the 16th minute of the Victory's Round 8 clash with the Western Sydney Wanderers at Parramatta Stadium, Gallagher was controversially sent off for bringing down Wanderers striker Dino Kresinger just outside the penalty area, denying the Croatian what was deemed an obvious goalscoring opportunity.

As a result of that red card, Gallagher was handed a one match ban, ruling him out of the Victory's clash with Perth Glory.

[12] Gallagher, along with teammates Diogo Ferreira, Spase Dilevski and Tando Velaphi were released by Melbourne Victory in April 2013, shortly after the end of the 2012–13 A-League season.

Four days after, Gallagher made his debut in the AFC Champions League as T&T played the first-round qualifier against Pune F.C.

[18] After being axed by Newcastle, Gallagher was picked up by Manly United halfway through the NSW NPL 1 season, making his debut in a heavy 4–0 defeat to Rockdale City Suns.

[21] Gallagher has represented Australia at the Under 19 and Under 20 levels, playing in the 2010 AFC U-19 Championship qualification and 2009 FIFA U-20 World Cup.