2020 United States presidential election in Arizona

The 2020 United States presidential election in Arizona was held on Tuesday, November 3, 2020, as part of the 2020 United States presidential election, in which all 50 states and the District of Columbia participated. Arizona voters chose 11 electors to represent them in the Electoral College via a popular vote pitting incumbent Republican President Donald Trump of Florida and his running mate, incumbent Vice President Mike Pence of Indiana, against Democratic challenger and former Vice President Joe Biden of Delaware and his running mate, United States Senator Kamala Harris of California. The Libertarian nominees were also on the ballot.

Trump carried Arizona in 2016 by 3.5%, and it was considered a vital battleground in this election. The state's bitterly competitive nature was attributed to diversification of Maricopa County, a traditionally Republican stronghold that holds 61.6% of the state's population. Maricopa County was seen as vital to either candidate's chances in the state–only one presidential candidate has ever won the state without carrying it. Biden became the first Democrat to win Arizona since Bill Clinton in 1996, and only the second since Harry S. Truman in 1948. He is also the first Democrat to win Maricopa County since Truman, with a margin of 2.2%, or 45,109 votes. High turnout among Hispanic/Latino and Native American voters was also seen as vital. Polls of the state throughout the campaign generally showed a Biden lead, albeit by a slender margin. Prior to election day, 11 of the 16 news organizations considered that Arizona was leaning towards Biden; the other five considered it a toss-up.

Biden ultimately won the state by some 10,000 votes over Trump, a 0.3% margin, marking the first time a Democratic presidential nominee carried Arizona since Bill Clinton in 1996, and only the second time since Harry S. Truman's 1948 victory. Arizona was the second-closest state in 2020, the only closer state being Georgia, marking the first time since 1948 that the Democratic nominee won both Sun Belt states in the same presidential election (Clinton won each state in separate elections). This was also the first time since 1932 that a non-incumbent Democrat carried Arizona in a presidential election, or that an incumbent Republican lost the state. Arizona weighed in as 4.15 percentage points more Republican than the nation in 2020.

After the election, the Republican-majority Arizona Senate launched a Maricopa County-based publicly-funded investigation into the election fraud alleged by Trump and his supporters. The controversial audit, completed in September 2021, found no evidence to support claims of significant election irregularities. Additionally, the count taken in audit gave Biden a greater lead of 360 votes over Trump than what the earlier, certified results had given.