The Alberta New Democratic Party (Alberta NDP; French: Nouveau Parti démocratique de l'Alberta), is a social democratic political party in Alberta, Canada. The party sits on the centre-left to left-wing of the political spectrum and is the provincial Alberta affiliate of the federal New Democratic Party.

The successor to the Alberta section of the Co-operative Commonwealth Federation and the even earlier Alberta wing of the Canadian Labour Party and the United Farmers of Alberta. From the mid-1980s to 2004, the party abbreviated its name as the "New Democrats" (ND).

The party served as Official Opposition in the Legislative Assembly of Alberta from 1982 to 1993. It was shut out of the legislature following the 1993 election, returning in the 1997 election with two seats. The party won no more than four seats in subsequent elections until the 2015 election, in which it won 54 of the 87 seats in the legislature and formed a majority government. Until 2015, Alberta had been the only province in western Canada—the party's birthplace—where the NDP had never governed at the provincial level. The Alberta NDP was defeated after a single term in the 2019 election by the United Conservative Party—the first time that a governing party in Alberta had been unseated after a single term.

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The Co-operative Commonwealth Federation (CCF) was founded in Calgary on 1 August 1932. However, it faced challenges in Alberta due to lack of support from the governing United Farmers of Alberta party and the Labour Party. While some UFA Members of Parliament supported the CCF and ran unsuccessfully as CCF candidates in the 1935 federal election, most UFA leaders and members were ambivalent. The CCF did not run candidates in the 1935 provincial election due to its ties with the UFA and Labour Party. The UFA lost all its seats in the election, and CCF candidates associated with the UFA were defeated due to the unpopularity of the UFA government and the rising popularity of William Aberhart's Social Credit movement.

In 1936, William Irvine, a CCF founder and defeated UFA Member of Parliament, was elected the Alberta CCF's first president. In 1937, the UFA decided to leave electoral politics entirely and, in 1938, the CCF committed itself to run candidates in the next provincial and elections setting up local riding clubs for that purpose. In 1939, former UFA/CCF MLA Chester Ronning became the Alberta CCF's first leader in the 1940 provincial election but despite winning 11% of the vote the party did not win any seats in the Alberta Legislature - the CCF had not garnered the support of the UFA's conservative supporters or put a dent in support for the agrarian populism of the Social Credit Party of Alberta.

The Alberta wing of the Labour Party federated with the CCF in 1935, but ran its own candidates in the 1935 and 1940 provincial elections. In 1942, the Alberta CCF clubs formally merged with the Labour Party and Elmer Roper became the new leader after achieving an unexpected victory in a 1942 by-election, becoming the party's first Alberta MLA (excepting Chester Ronning, who had been elected in 1932 as a joint UFA/CCF candidate). In the next two years party membership soared from 2,500 to over 12,000.

In the 1944 election, the CCF received 24% of the vote but won only 2 seats, both of them in Edmonton and Calgary where the use of single transferable vote ensured fair representation. (The disproportionality was due to the way boundaries of the constituencies outside the cities were drawn and the use of Instant-runoff voting outside the cities, which did not help a lesser party like the CCF.) The Social Credit government received more than half of ballots cast. Roper was joined in the legislature by Aylmer Liesemer, a Calgary schoolteacher. The rise of support for the CCF after 1942 mobilized the business community to pull out of efforts to build an anti-Social Credit party and instead back the Social Credit government, now led by Ernest Manning, after William Aberhart's death in 1943, as a bulwark against socialists. Unlike the Saskatchewan CCF, which won office in the 1944 Saskatchewan election on a platform calling for social programs, the Alberta CCF was more radical and campaigned on provincial ownership of the province's resources and utilities. Irvine also advocated an alliance with the communist Labor-Progressive Party which would have been beneficial in the cities where the single transferable vote electoral system was used.