Lars K. Aaker (September 9, 1825 – August 14, 1895) was an American farmer and politician.
Born in Lårdal, Telemark, Norway, Aaker emigrated to the United States in 1845 and lived in Dane County, Wisconsin Territory. In 1847, Aaker moved to Goodhue County, Minnesota Territory and then to Alexandria, Minnesota in 1870. Aaker was a farmer and in the mercantile business. During the American Civil War, Aaker served in the 3rd Minnesota Volunteer Infantry Regiment. He worked in the United States Land Office in Alexandria, Minnesota from 1870 to 1876 and then in Crookston, Minnesota from 1883 to 1893. In 1859-1860, 1862, 1867, and 1869, Aaker served in the Minnesota House of Representatives and was a Republican. In 1881 and 1882, Aaker served in Minnesota State Senate. Aaker died from a stroke at his home in Alexandria, Minnesota.