Effingham Lawrence (March 2, 1820 – December 9, 1878) was an American politician known for serving for the shortest term in congressional history, serving—along with George A. Sheridan—for just one day in the U.S. House of Representatives.
He served in the Louisiana State House of Representatives for some time and then successfully contested the re-election of Jacob Hale Sypher.
Lawrence's belated replacement of Sypher, after courts intervened to nullify the original results and instead deliver the seat to Lawrence, marked the first time since the Civil War that a Democrat had defeated a Republican for a seat in Congress from Louisiana.
Thus, under the congressional calendar in effect at the time, Lawrence was able to serve for one day of the 1873–1875 term to which he had, in the end, been elected.
On the following day—March 4, 1875—he was succeeded by Randall Lee Gibson, a Democrat who had defeated him during the preceding autumn.