Essi Katriina Sainio (born 9 September 1986) is a Finnish former professional footballer, who last played for HJK in Finland as a winger.

Sainio began her senior career with Naisten Liiga clubs FC Honka and HJK in her home country.

Since making her debut in 2006, Sainio has won 45 caps and scored three goals for the Finland women's national football team.

A winger who can also play as a full-back,[5] she was part of the Finnish team which hosted UEFA Women's Euro 2009 and reached the quarter-finals.

[9] National coach Michael Käld selected Sainio in the squad for UEFA Women's Euro 2009, which Finland were hosting.