Robert McKnight (January 20, 1820 – October 25, 1885) was a Republican United States Representative from Pennsylvania. Robert McKnight was born in Pittsburgh, Pennsylvania. He attended the common schools and a private school at Xenia, Ohio. He graduated from Princeton College in 1839. He studied law, was admitted to the bar in 1842 and commenced practice in Pittsburgh. He was city councilman from 1847 to 1849.