Andrea Horwath is a politician in Ontario, Canada. She is currently a member of the Legislative Assembly of Ontario, representing the riding of Hamilton East for the Ontario New Democratic Party.

Horwath was born and raised in Hamilton, Ontario, and has a Bachelor of Arts degree in Labour Studies from McMaster University in that city. She received her first job as a community development worker at the McQueston Legal Clinic, providing assistance to workers in the city.

In the Canadian general election of 1997, she challenged incumbent Liberal Stan Keyes in the riding of Hamilton West. Although unsuccessful, her second-place finish was a significant improvement on previous NDP efforts in the riding, and gave her an increased level of prominence in the city. Later in the year, she was elected to the Hamilton City Council for Ward Two (in the downtown core), outpolling two incumbents who had represented the area for more than twenty years. She emerged as a prominent voice for the political left in the city, and was re-elected to council in 2000 and 2003.

Horwath was elected to the Legislative Assembly of Ontario in a 2004 by-election in the riding of Hamilton East, defeating Liberal candidate Ralph Agostino to succeed the deceased Liberal member Dominic Agostino, Ralph's brother. Her landslide victory gave the NDP official party status in the legislature and helped give the NDP a bounce in Hamilton that would continue into the federal election shortly thereafter.

Horwath is generally regarded as being on the left-wing of her party.

By-election results

May 13, 2004

1. Andrea Horwath, NDP 15,185 (63.6%)
2. Ralph Agostino , Liberal 6,362 (26.6%)
3. Tara Crugnale , Prog. Cons. 1,772 (7.4%)
4. Raymond Dartsch , Green 448 (1.9%)
5. John C. Turmel, Independent 120 (0.5%)