Gardner Colby (1810–1879) was a prominent businessman and Christian philanthropist.

His father, Josiah Colby, died in 1814 after having lost his fortune during the War of 1812, and Josiah Colby had spent time manufacturing gunpowder in Waterville before his death.

Gardner Colby eventually started his own store in Boston and became involved in various other businesses including railroads, shipping and manufacturing.

During the Civil War in 1864 the college in Waterville was facing hardships, so Colby made the first of several large donations to the college and it was subsequently renamed "Colby University" in his honor.

Colby also served as treasurer and made several large donations to what is now Andover Newton Theological School, which was a Reformed seminary located near Colby's home in Newton, Massachusetts.