William Hollis Long II, born August 11, 1955, is an American politician and auctioneer. He currently serves as the United States Ambassador to Iceland, a position he has held since August 2026. Prior to this diplomatic role, Long was the 51st commissioner of internal revenue from June to August 2025.

A member of the Republican Party, he also represented Missouri's 7th congressional district as a U.S. Representative from 2011 to 2023.