Robert "Romeo" Coates (1772 – 21 February 1848) was an English eccentric, best remembered for his career as an amateur actor. His self-image included a highly mistaken belief in his own thespian prowess. Born in Antigua in the West Indies and educated in England, he began to appear in plays in Bath in 1809, and became notorious for his fondness for appearing in leading roles. His favourite part was the male lead in Shakespeare's Romeo and Juliet, hence his widely used nickname. After professional theatrical producers failed to cast Coates in roles prominent enough to satisfy him, he used his family fortune to subsidise his own productions in which he was both the producer and the lead actor.

Coates claimed to be the best actor in Britain. He would appear in bizarre costumes of his own design, invent new scenes and dialogue mid-show, and repeat parts of the play he particularly liked—usually dramatic death scenes—up to three or four times a night. His fame quickly spread and people flocked to see whether Coates was really as bad as they had heard. They laughed, jeered, and pelted (i.e. threw things at) him; Coates sometimes turned to the audience and answered in kind. By 1816 audiences had tired of mocking Coates, and theatre managers were no longer willing to let him use their premises. After some years living in France to avoid creditors, he returned to England, married in 1823, and had two children who both predeceased him. Coates died in London in 1848, aged about 76, after a Hansom cab driver hit him outside the Theatre Royal, Drury Lane.

Robert Coates was born in Antigua in the West Indies, the only surviving child of a wealthy sugar planter, Alexander Coates, and his wife Dorothy. He was educated in England, and on returning to Antigua took part in amateur dramatics. When he inherited his father's estate and a large collection of diamonds in 1807, he moved to Bath, England, where he lived as a man of fashion. He eventually drew the attention of the manager of the Theatre Royal, Bath and had begun to appear in plays in 1809, though not as a professional actor.

Later he appeared in Romeo and Juliet in the part of Romeo – in a costume of his own design. The costume had a flowing, sky-blue cloak with sequins, red pantaloons, a vest of white muslin, a large cravat, and a plumed "opera hat," according to Captain Rees Howell Gronow – not to mention dozens of diamonds – which was hardly suitable for the part. The garments were too small for Coates and caused him to move stiffly, and at some point, the seat of his pants split open. The audience roared with laughter.

Despite this ridicule, Coates went on to tour the British Isles. If a theatre manager would hesitate to let him show his talents, he would bribe them. Managers, in turn, often called in the police in case things went seriously wrong.

Coates was convinced he was the best actor in business – or at least that is what he claimed. He frequently forgot his lines and invented new scenes and dialogue on the spot. He loved dramatic death scenes and would repeat them – or any other scenes he happened to take a fancy to – three to four times over.

Coates claimed that he wanted to improve the classics. At the end of his first appearance as Romeo he came back in with a crowbar and tried to pry open Capulet's tomb. In another of his antics he made the actress playing Juliet so embarrassed that she clung to a pillar and refused to leave the stage. Eventually no actress would agree to play the part with him.

The audience usually answered with angered catcalls, embarrassed jeering, and a large pelting of orange peels – and loads of laughter. His fellow actors would try to make him leave the stage. If Coates thought the audience was getting out of hand, he turned to them and answered in kind.