Alexander Mack Aikin Jr. (October 9, 1905 – October 24, 1981) was an American politician who served in the Texas House of Representatives and the Texas Senate as a Democrat. He was elected to the House of Representatives in 1932, and after serving two terms was elected to the Senate in 1937. In total, he served for 46 years in the two chambers of the Texas Legislature, making him the longest-tenured legislator in the history of Texas at the time of his retirement in January 1979.