Spencer John Kieboom
- Bats Right, Throws Right
- Height 6' 0", Weight 210 lb.
- School Clemson University
- High School George Walton Comprehensive High School
- Debut October 2, 2016
- Final Game September 30, 2018
- Born March 16, 1991 in Mount Pleasant, SC USA
Spencer Kieboom was the 257th and last player to make his major league debut in 2016, doing so as a pinch-hitter with the Washington Nationals on the final day of the regular season, October 2nd. Batting in place of Sammy Solis in the 8th, he drew a walk off Brian Ellington of the Miami Marlins and came in to score on a single by Ben Revere.
He spent all of 2017 in the minors, hitting .250 in 66 games between the AA Harrisburg Senators and AAA Syracuse Chiefs in a season marred by injuries. In 2018 however, he returned to the Show to play 52 games for Washington, during which he hit .232 with 2 homers and 13 RBIs as a back-up to C Matt Wieters. He had started the season with Syracuse, where he hit .250 in 25 games before being called up in mid-May.
His younger brother, IF Carter Kieboom, was drafted by the Nationals in the supplemental 1st round of the 2016 amateur draft and made his debut with the Nats in 2019. Spencer had been a 5th round selection in the 2012 amateur draft. His father Alswinn Kieboom had played in the Hoofdklasse.