Irene R. Mathyssen (born August 16, 1951) is a Canadian politician and was a Member of Parliament in the House of Commons of Canada from 2006 until 2019.

She was previously a New Democratic Party Member of Provincial Parliament (MPP) in Ontario from 1990 to 1995, and briefly served as a minister in the government of Premier Bob Rae.

In that capacity she announced that 6 million dollars would be spent on the cleanup of beaches in rural areas which were closed mostly due to agricultural runoff issues.

[17] On January 1, 2012, Caterpillar Inc. locked out over 450 workers from the Electro Motive Diesel plant in Mathyssen’s riding of London-Fanshawe.

The idea gained popular grassroots support, with a group called Canadian Menstruators organizing an online petition that rapidly attracted tens of thousands of signatures from across Canada.

[20] Mathyssen took the lead in the House of Commons for an NDP Opposition Day, introducing a motion to force a vote on the issue.

The governing Conservatives initially tried to stall the effort promising to revisit the idea in the future, without a clear timeline.

Mathyssen would not relent however, and with more than 74,000 Canadians having signed the petition, the Conservatives, with pressure mounting from their own female MPs threatening to not show up for the vote, changed course at the last moment.

[21] With the backing of MPs from all political parties in the House of Commons, Mathyssen's motion passed and the tax was eliminated on July 1, 2015.

Despite a strong "Stop Harper" campaign that led to increased voter turnout and sent a wave of popular support to Justin Trudeau's Liberals at the expense of the NDP, Mathyssen not only held her seat in London-Fanshawe, but retained almost all of the 20,000+ votes she received in 2011.

NDP leader Tom Mulcair named Mathyssen the party's Critic for Veterans Affairs and the deputy whip for the caucus.