The 2003 New Democratic Party leadership race to replace New Democratic Party of Canada leader Alexa McDonough ended January 25, 2003 with the first ballot victory of popular Toronto city councillor Jack Layton.

The leadership race was the first to be conducted under the NDP's new partial one member, one vote system, in which the popular vote of the members is weighted for 75% of the result. The rest are votes cast by delegates for affiliated organizations (mainly labour unions). It was also the first Canadian leadership convention to allow Internet voting; delegates who chose to vote electronically were given a password to a secure website to register their votes.

The race was heated, with the leaders campaigning to NDP audiences across Canada. One of the most notable events of the campaign occurred at the convention in Toronto, when candidate Pierre Ducasse made a stirring speech that resulted in several prominent changes of allegiance and was hailed as one of the best NDP speeches since the days of Tommy Douglas. It was speculated that if the great majority of New Democrats hadn't voted electronically and by mail before convention, he would have obtained a much higher percentage of the vote on the strength of that speech alone.

Candidates

• Jack Layton - former Toronto City Councillor (winner, 53.5%)
• Bill Blaikie - Member of Parliament (24.7%)
• Lorne Nystrom - Member of Parliament (9.3%)
• Joe Comartin - Member of Parliament (7.7%)
• Pierre Ducasse - Associate President of the NDP (3.7%)
• Bev Meslo - feminist/socialist, representing the NDP Socialist Caucus (1.1%)