2015 Alberta general election

The 2015 Alberta general election was held on May 5, following a request of Premier Jim Prentice to the Lieutenant Governor of Alberta Donald Ethell to dissolve the Legislative Assembly on April 7. This election elected members to the 29th Alberta Legislature. It was only the fourth time in provincial history that saw a change of governing party, and was the last provincial election for both the Alberta Progressive Conservative and Wildrose parties, which merged in 2017 to form the United Conservative Party (although each ran a token candidate in the 2019 election).

The provincial Election Act fixed the election date to a three-month period between March 1 and May 31 in the fourth calendar year after the preceding election day – in this case, April 23, 2012. However, the act does not affect the powers of the Lieutenant Governor to dissolve the Legislature before this period.

As a result of the election, the Alberta New Democratic Party (NDP) were elected to a majority government under leader Rachel Notley. The NDP formed government for the first time in Alberta history since the NDP's founding in the early 1960s.

The 2015 election is sometimes called the "Orange Chinook", a reference to the province's dramatic swing to the NDP, the NDP's orange colour and the weather shifts occasioned by strong Chinook winds that southern Alberta commonly experiences.

The NDP win ousted the PCs, who were reduced to third place in seats. Prentice resigned as PC leader and MLA for Calgary-Foothills on election night.

The Progressive Conservatives (PCs) had a majority in the outgoing Assembly and had won every provincial election since the 1971 election, making them the longest-serving provincial government in Canadian history – being in office for 44 years. This was only the fourth change of governing party in Alberta since becoming a province in 1905, and one of the worst defeats a provincial government has suffered in Canada. 31 PC MLAs lost re-election to the legislature, the largest number in one election in Alberta history. It also marked the first time in almost 80 years that a left-of-centre political party had formed government in Alberta since the defeat of the United Farmers of Alberta in 1935 and the Depression-era radical monetary reform policies of William Aberhart's Social Credit government.

The Wildrose Party under leader Brian Jean remained the Official Opposition, gaining four seats since 2012 despite winning 81,814 fewer votes and a 10.1% lower share of the popular vote than in the previous election. The Alberta Liberal Party and Alberta Party each won a single seat with Alberta Party leader Greg Clark becoming the party's first MLA. The Alberta Liberal Party lost four seats, only returning interim leader David Swann to the Legislative Assembly.

Following the election, Notley and her cabinet were sworn in on May 24.

Overall, across the province, 1,488,248 valid votes were cast in this election.