Allen Lucas Messer (born February 27, 1969) is an American politician and lobbyist who represented Indiana's 6th congressional district in the United States House of Representatives from 2013 to 2019. He is a member of the Republican Party.

Born in Evansville, Indiana, Messer is a graduate of Wabash College and Vanderbilt University Law School. After an unsuccessful run for the U.S. House in 2000, Messer served as the first executive director of the Indiana Republican Party from 2001 to 2005. Messer was appointed to serve in the Indiana House of Representatives in 2003, after State Representative W. Roland Stine was killed in a car accident. He represented Indiana's 57th District from 2003 to 2006, when he opted not to run for reelection and instead joined Ice Miller LLP's lobbying division. From 2006 to 2012, Messer was a registered lobbyist. He ran for the U.S. House again in 2010, but was unsuccessful in his primary challenge to Republican Dan Burton. When Mike Pence decided in 2012 to run for Governor of Indiana, Messer was elected to replace him, defeating Democratic nominee Brad Bookout.

On July 26, 2017, Messer announced that he would run for the U.S. Senate in 2018. He was unsuccessful in the May 8 primary election, losing to Mike Braun.

Messer graduated from Greensburg Community High School in 1987. Messer attended Wabash College where he was a member of the Phi Delta Theta fraternity and majored in speech. He graduated in 1991. He received a Juris Doctor from Vanderbilt University Law School in 1994. Shortly after graduating from Vanderbilt, he served as an Associate Counsel at Koch Industries from 1995 to 1996.

Messer started his political career in 1997 as the press secretary for Tennessee Representative Ed Bryant. He was the legal counsel on the House Subcommittee for Government Reform for Indiana Representatives David McIntosh and Dan Burton from 1998 to 1999, and the legal counsel to U.S. Representative Jim Duncan later in 1999. In 1998, he was the campaign manager for Virginia Murphy Blankenbaker's unsuccessful congressional campaign. In 1999, Messer returned to Indiana and practiced law at the Barnes & Thornburg law firm in Indianapolis.

In 2000, Messer ran for the United States House of Representatives in Indiana's 2nd congressional district, where incumbent David M. McIntosh was retiring to run for governor of Indiana in the 2000 election. Messer received the endorsement of The Indianapolis Star. He received 21 percent of the vote in the Republican Party's primary election, finishing behind conservative talk show host Mike Pence, who won with 44 percent of the vote, and Jeff Linder, who received 24 percent of the vote. In 2001, Messer was chosen as the executive director of the Indiana Republican Party.

On May 23, 2003, Messer was selected to succeed W. Roland Stine, who died in a traffic collision, in the Indiana House of Representatives for the 57th district. From 2003 to 2006, Messer represented District 57 in the Indiana House of Representatives, which contained parts of Shelby County and Bartholomew County. During the 2005-06 legislative session, Messer was Assistant Majority Floor Leader. His legislation aimed at curbing high school dropout rates received national attention after Shelbyville High School became a symbol of a national dropout crisis. He did not run for reelection as State Representative in 2006, and was succeeded by Sean Eberhart.

Messer was a registered lobbyist from 2006 to 2012.