Lewis S. Wisner (August 11, 1841 - October 6, 1906) was an American soldier and recipient of the Medal of Honor who fought in the American Civil War.

Lewis Wisner was born on August 11, 1841, in Wallkill, New York. After enlisting on August 12, 1862, he served in 124th New York Volunteer Infantry Regiment starting as a sergeant on September 5, 1862. He had reached the rank of First Lieutenant by his Medal of Honor action at the Battle of Spotsylvania Court House, Virginia on May 12, 1864. He was awarded the Medal of Honor on January 2, 1895 for his bravery during the Battle of Spotsylvania Court House.

He died on October 6, 1906 in Middletown, New York, and is now buried in Hillside Cemetery, Middletown, New York.

For extraordinary heroism on 12 May 1864, in action at Spotsylvania, Virginia, while serving as an engineer officer voluntarily exposed himself to the enemy's fire.