Patrick Cotter O'Brien (19 January 1760 – 8 September 1806) was the first of only thirteen people in medical history to stand at a verified height of eight feet (2.44 m) or more. O'Brien was born in Kinsale, County Cork, Ireland. His real name was Patrick Cotter and he adopted O'Brien as his stage name in the sideshow circuit. He was also known as the Bristol Giant and the Irish Giant.

It is believed he died from the effects of the disease gigantism.

No hearse could be found to accommodate his nine feet four inch casket encased in lead, and his remains were borne to the grave by relays of fourteen men. In his will, Cotter left £2,000 to his mother and a request that his body be entombed within twelve feet of solid rock (to prevent exhumation for scientific or medical research).

In 1972 his remains were examined and it was determined that, while alive, he stood approximately 8 feet 1 inch (246 cm) tall. This made him the tallest person alive at that time, a record that would be surpassed by the next 'eight-footer', John Rogan, who died almost a century later. Patrick Cotter's giant boots are on display in the Kinsale Museum.

An arm of Cotter's is currently preserved in the Medical Museum of the Royal College of Surgeons, London.