Edgar Cowan (September 19, 1815 – August 31, 1885) was an American lawyer and Republican politician from Greensburg, Pennsylvania. He represented Pennsylvania in the United States Senate during the American Civil War.
Cowan was born in Westmoreland County, Pennsylvania. He graduated from Franklin College, Ohio, in 1839 and subsequently became a raftsman, boat builder, schoolmaster, and a student of medicine. He studied law, was admitted to the bar and commenced practice in Greensburg, Pennsylvania, in 1842. He was elected as a Republican to the United States Senate and served from March 4, 1861, to March 3, 1867, and was an unsuccessful candidate for reelection to the Senate. During his tenure in office, he served as chairman, Committee on Patents and the Patent Office (Thirty-seventh through Thirty-ninth Congresses). Following the Civil War, he was appointed by President Andrew Johnson as Minister to Austria in January 1867, but was not confirmed by the Senate. He then resumed the practice of law.
Cowan died in Greensburg and was buried in St. Clair Cemetery.