George Golding Kennedy was born on October 16, 1841, in Roxbury, Suffolk, Massachusetts.

He was a physician, businessman, and botanist. He was educated at Roxbury Latin School. He graduated from Harvard in 1864 and received his M.D. degree from Harvard Medical School in 1867. After practicing medicine for a short time, he took over his father's business of manufacturing medicines, an occupation that allowed him to acquire considerable wealth while leaving him with enough leisure to carry out his own studies. He studied botany under Asa Gray at Harvard and maintained a life-long interest in the subject. In 1896, he was one of the founders of the New England Botanical Club. He developed a sizeable herbarium which he eventually gave to the Farlow, Gray, and New England Botanical Club herbaria. He was active on the Visiting Committee of the Gray Herbarium and gave the money to build a new library wing in 1914. Kennedy also had a strong background in the classics and was a collector of rare books. He did much work on a detailed index of plants in the works of Bacon and Shakespeare, with notes on the historic uses of the plants, which appears not to have been completed or published.

In 1865, he married Harriet White Harris (1835–1910). He died on March 31, 1918, in Milton, Norfolk, Massachusetts.