Ronnie and Donnie Galyon (October 28, 1951 – July 4, 2020) were American conjoined twins.

Known for - Oldest living set of conjoined twins.

According to the 2009 Guinness World Records, the Galyons were the oldest living set of conjoined twins in the world, and, as of 29 October 2014, possess the world record for the longest-lived conjoined twins in history when they surpassed prior record holders Giacomo and Giovanni Battista Tocci.

They were born at St. Elizabeth Hospital in Dayton, Ohio, on October 28, 1951, to Wesley and Eileen Galyon. Eileen was not expecting twins. They were joined from the sternum to the groin and shared a set of organs. After a two-year stay in the hospital, it was determined that they could not be safely separated. Local schools deemed the twins a distraction, so they were not formally educated, resulting in their lifelong functional illiteracy.

With nine children to support, their father Wesley decided to take the twins on the road as a sideshow attraction. The boys were exhibited in sideshows throughout the U.S. and later in Latin America. Their tours made them celebrities and provided an income with which they supported their family. The twins also tried to join the Army, but were ranked 4-F.

In 1991, after three decades in entertainment, the pair retired and moved into their first independent home in Dayton, Ohio, in a house purchased with sideshow earnings. They were active in the community and lived a largely normal life by means of a custom double wheelchair. Although retired from show business, the twins made numerous television appearances. They appeared on The Jerry Springer Show in 1997, a Discovery Channel documentary in 1998 and a Channel Five documentary in 2009.

In 2009, Ronnie developed a life-threatening infection in his lungs, which quickly endangered both twins. After their hospitalization, they required round-the-clock care. Their younger brother Jim and his wife Mary, who lived in the same city, were unable to bring the twins into their home as it was not handicap accessible, until an outpouring of donations and volunteers from the local community assisted in building a special addition to the home. On December 22, 2010, TLC premiered "The World's Oldest Conjoined Twins Move Home," which documented the building process as well as the twins' recovery and their return to the community.

The twins died in hospice in their native Dayton, Ohio on July 4, 2020.