Cowan, Mo, 1969-

William Maurice "Mo" Cowan (born April 4, 1969) is an American lawyer who served as a United States Senator from Massachusetts from February 1, 2013, to July 16, 2013. He is a member of the Democratic Party.

A native of Yadkinville, North Carolina, Cowan earned an AB degree from Duke University in 1991. Moving north, Cowan attended Northeatern University School of Law, graduating with a JD in 1994. He remained in Boston where he joined several reputable law firms as a litigation associate, and then as partner until 2009. From 2009 to 2011, Cowan advised Massachusetts Governor Deval Patrick on a host of issues including legislation and policy, the appointment of judges, and general legal matters. In 2011 he became Patrick’s chief of staff and in 2013 his senior advisor. When John Kerry accepted his appointment as Secretary of State in Barack Obama's second term and resigned from the Senate, Governor Patrick chose Cowan to fill the vacancy, making him the interim Massachusetts Senator.

Cowan declined to run in the 2013 special election to complete the remainder of Kerry's term. He was succeeded by fellow Democrat Ed Markey. Cowan was the eighth African-American U.S. Senator and the second from Massachusetts after Edward Brooke. After leaving office, Cowan returned to Boston to be with his family and continue his law career.