William A. Halter Jr is an American politician who served as the 18th lieutenant governor of Arkansas from 2007 to 2011. A member of the Democratic Party, he was elected to succeed the late Republican Winthrop Paul Rockefeller in 2006, defeating Republican challenger Jim Holt.

The lieutenant governor of Arkansas presides over the Arkansas Senate with a tie-breaking vote, serves as acting governor of Arkansas when the governor is out of state and assumes the governorship in cases of impeachment, removal from office, death or inability to discharge the office's duties. The position is elected separately from the Arkansas Governor.