John Barrasso, a conservative Republican state senator, was named as the country's newest U.S. senator to succeed the late Craig Thomas.
The temporary appointment, announced by Wyoming's governor, is immediate but won't change the Senate's party breakdown since Thomas was also a Republican.
Thomas died June 4 while being treated for leukemia.
Barrasso, 54, will serve until the beginning of 2009.
The orthopedic surgeon from Casper said on his application that he also intends to run in a November 2008 special election to serve out the remainder of Thomas' term, which would have ended in 2013.