William W. Mercer

Bill Mercer
Judge of the United States District Court for the District of Montana
Assumed office
November 6, 2025
Appointed byDonald Trump
Preceded byDana L. Christensen
Acting United States Associate Attorney General
In office
March 17, 2006 – June 22, 2007
PresidentGeorge W. Bush
Preceded byRobert McCallum Jr.
Succeeded byGregory G. Katsas (acting)
United States Attorney for the District of Montana
In office
April 20, 2001 – December 30, 2009
PresidentGeorge W. Bush
Preceded bySherry Scheel Matteucci
Succeeded byMichael W. Cotter
Member of the Montana House of Representatives
from the 52nd district
In office
January 6, 2025 – November 10, 2025
Preceded bySherry Essmann (redistricting)
Succeeded byStacy Zinn
Member of the Montana House of Representatives
from the 46th district
In office
January 7, 2019 – January 6, 2025
Preceded byDon Jones
Succeeded byDenise Joy (redistricting)
Personal details
Born1964 (age 61–62)
PartyRepublican
SpouseMarci Mercer
Children2
EducationUniversity of Montana (BA)
Harvard University (MPA)
George Mason University (JD)

William Walter "Bill" Mercer (born 1964) is an American attorney and politician serving as a United States district judge of the United States District Court for the District of Montana. He served as a member of the Montana House of Representatives from 2019 to 2025. He previously served as the United States attorney for the District of Montana, as well as principal associate deputy attorney general for the United States Department of Justice. Mercer was nominated by President George W. Bush as Associate Attorney General and served in the position in an acting capacity. He resigned before his confirmation hearing could take place.