Terrance William Gainer (born August 1, 1947) is a former law enforcement officer and was the 38th Sergeant at Arms of the United States Senate[2] and served in that position from January 4, 2007, to May 2, 2014.

Before Gainer continued his law enforcement career in Washington, D.C., he was the Republican candidate for Cook County State's Attorney in the 1988 election, losing to then-incumbent Richard M.

[7] During his law enforcement career, Gainer served with the Chicago Police Department[8] as deputy Inspector General of Illinois, deputy director of the Illinois State Police and in the United States Department of Transportation[7] before he was appointed as director of the Illinois State Police in the Cabinet of Governor Jim Edgar in March 1991.

[11] In addition, Gainer served as the Director of Emergency Preparedness for The Nonprofit Roundtable of Greater Washington.

During his time with the Nonprofit Roundtable of Greater Washington, Gainer worked extensively with non-profit organizations (such as hospitals, schools and charities) to help them formulate a coordinated response for emergency preparedness in the Washington, DC metropolitan region.