Thomas Charles O'Halleran (/oʊˈhælərən/; born January 24, 1946) is an American politician who served as the U.S. representative for Arizona's 1st congressional district from 2017 to 2023.

[9] In May 2016, O'Halleran was named to the Democratic Congressional Campaign Committee's Red to Blue list, indicating that his race was a priority for the group.

[11] He defeated Republican Paul Babeu and Green Party candidate Ray Parrish[12] in the general election[13] with 51% of the vote.

[19] O'Halleran lost to Crane in the general election, winning only in the district's most Democratic counties, Coconino and Apache.

He voted in support of a resolution calling for Vice President Mike Pence to use the Twenty-fifth Amendment to the United States Constitution to remove Trump from office.

[29] O'Halleran opposed the 2022 overturning of Roe v. Wade, calling it "a mammoth setback for women, families and our nation.

"[30] According to On the Issues, in 2008 O'Halleran introduced HB 2613, an act that would give businesses using renewable energy property tax incentives.

[33] After the Stoneman Douglas High School shooting in Parkland, Florida, O'Halleran, who had long supported expanded background checks but opposed an assault-weapon ban, suggested he might shift toward a stronger position on gun control.

[35] In April 2017, O'Halleran criticized Attorney General Jeff Sessions's tougher new guidelines on expelling illegal immigrants who belong to criminal gangs.

[41] On June 7, 2023, O'Halleran was named Senior Advisor for the Natural Resources Conservation Service of the U.S. Department of Agriculture.