Lydia Grace Yilkari Williams (born 13 May 1988) is an Australian soccer player who currently plays as a goalkeeper for Arsenal in England's FA Women's Super League (WSL) and the Australia women's national soccer team. She previously played for Melbourne City and Canberra United in Australia's W-League; Reign FC, Houston Dash and the Western New York Flash in the National Women's Soccer League (NWSL) in the United States; and Pitea IF in Sweden's Damallsvenskan.
Williams was twice-named PFA Women's Footballer of the Year for 2011–12 and 2015–16 and to the PFA W-League Team of the Season for 2016–17. She was awarded W-League Goalkeeper of the Year for the 2010–11, 2011–12, and 2016–17 seasons.
Inducted to the Aboriginal and Islander Sports Hall of Fame, Williams earned for her first cap for the Australian national team, commonly known as the Matildas, at age 16. She is the author of the children's book, Saved!!!, published in 2019.