Dr. Reuben Samuel (January 12, 1828 – March 1, 1908) was the stepfather of the American outlaws Frank and Jesse James.

The third husband of Frank and Jesse's mother, Zerelda Reuben, was the son of Fielding and Louisa Samuel, and was 27 years old when he married Zerelda on September 25, 1855. He was described as a "quiet, passive man". He left behind the medical profession upon marrying Zerelda and moved onto a farm, raised tobacco, and supposedly acquired a total of seven slaves by 1860. He took on Zerelda's three living children, Frank, Jesse, and Susan, as well as having four more with Zerelda:

• Sarah Ellen "Sallie" Samuel (born April 7, 1858)
• John Thomas Samuel (December 25, 1861)
• Fanny Quantrill Samuel (October 18, 1863)
• Archie Peyton Samuel (July 26, 1866)

In addition to those seven, one Perry Samuel was born to a former slave of the Doctor's in 1866. While it was never known who the biological father was, some believe it was Dr. Samuel.

Then came the Civil War. Militiamen searching for Frank James (who had joined the South) raided the Samuel farm, and briefly (though not fatally) hanged Dr. Samuel, torturing him to reveal the location of the guerrillas. Shortly afterward, Frank joined Quantrill's band in the August 21, 1863 Lawrence Massacre.

Some of Reuben Samuel's family still live in the Kansas City, MO area.