Thomas Erby Kilby Sr. (July 9, 1865 – October 22, 1943) was an American politician. He was the eighth lieutenant governor of Alabama and the 36th governor of Alabama.

Kilby was born in Lebanon, Tennessee, and was educated in public schools. In 1887, he was an agent for the Georgia-Pacific Railroad in Anniston, Alabama. He became a successful businessman in the industrial and banking business.

He was a Democratic politician and served as mayor of Anniston, Alabama from 1905 to 1909. He served as Alabama State Senator from 1911 to 1915.

Kilby served as Lieutenant Governor of Alabama from 1915 to 1919 and as Governor of Alabama from 1919 to 1923 In September 1919 two Black men Miles Phifer and Robert Crosky were arrested over allegations they assaulted two white women in separate incidents in Montgomery, Alabama. A mob quickly formed, and a concerned citizen notified Governor Thomas Kilby that there might be a lynching. Kilby ordered the two to be transferred to the relative safety of prison in Wetumpka, Alabama. Nevertheless, they were intercepted and lynched by a White mob on September 29, 1919.

In 1920, Kilby arbitrated the settlement of the lengthy and violent 1920 Alabama coal strike, ruling clearly against the demands of the United Mine Workers of America. The Child Welfare Department was created in 1919 during Kilby's governorship, while new labor laws were introduced.

Kilby married Mary Elizabeth Clark on June 5, 1894. They had three children.

Kilby House, their home in Anniston, Alabama, was built for Kilby while he was Lieutenant Governor. It is listed on the National Register of Historic Places.

Kilby died on October 22, 1943, in Anniston, Alabama at 78. He is buried at Highland Cemetery in Anniston.