William Yal was a Starfleet officer who served as XO on the USS Livingston in the 24th century.

Yal graduated from Starfleet Academy in 2354 with honors in probability and temporal mechanics. He served on many starships during his career, including two freighters in 2357 and a small Oberth-class vessel, the USS Gandhi for five years as a science officer.

In 2368, Commander Chakotay of the USS Livingston resigned his commission, which left the Livingston without a first officer. Yal had held the rank of lieutenant for five years and received a promotion to Lieutenant Commander. He became the new first officer in 2369 and served as XO until his death in 2382, while trying to save a convoy of Kellodian ships from destruction at the hand of the Cardassians. The Livingston was decommissioned the same year.