is a Canadian-born American professional soccer player who plays as a forward for Angel City FC of the National Women's Soccer League (NWSL).

Born in Canada to a Canadian mother (Sandi Leroux) and an American father (Ray Chadwick), Sydney came up through the Canadian system and represented Canada at various youth levels until she chose to play for the United States women's national under-20 soccer team starting in 2008 and later the U.S. senior national team starting in 2012. Leroux has earned over 75 caps with the senior national team and was part of the Americans' winning squads at the 2012 London Olympics and 2015 Women's World Cup.

Leroux played collegiate soccer in NCAA Division I for UCLA Bruins women's soccer and at the semi-professional level for the Vancouver Whitecaps. She made her debut for the Whitecaps at age 15, becoming the youngest player ever to play for the team. Leroux was the number one pick by the Atlanta Beat during the 2012 WPS Draft on January 13, 2012. Following the suspension of the league in early 2012, she played for the Seattle Sounders Women during the summer of the same year.

In 2013, she made her professional debut for the Boston Breakers in the NWSL during the league's inaugural season. She was later traded to Seattle Reign FC in 2014, Western New York Flash for the 2015 season and FC Kansas City prior to the 2016 season.