Squire John Trelawney is a supporting character from Robert Louis Stevenson's novel Treasure Island.

Stevenson describs him as a tall man, over six feet high, and broad in proportion, and he had a bluff, rough-and-ready face, all roughened and reddened and lined in his long travels. His eyebrows were very black, and moved readily, and this gave him a look of some temper, not bad, you would say, but quick and high.

The Squire is a bombastic and excitable landowner and friend to Dr. Livesey, another supporting character who has been sought out by the book's heroic protagonist, Jim Hawkins as a sanctuary from pirates who seek the treasure map that has fallen into Hawkins's possession.

Squire Trelawney immediately plans to commission a sailing vessel to hunt for the treasure, with the help of Dr. Livesey and Jim. He finances the entire expedition to the eponymous Treasure Island. Going to the Bristol docks, Trelawney buys the schooner Hispaniola, hires a Captain Smollett to command her, and retains Long John Silver, a former sea cook and now the owner of the dock-side "Spy-Glass" tavern, to run the galley. When it comes to hiring a crew for the ship the depends highly on the advice of Long John Silver who recruits a group of fellow pirates.

Livesey warns Trelawney to be silent about their objective, but he cannot keep a secret and everyone seems to get to know about the nature of the mission. Although the squire is financier of the expedition and appears to be the social better of all others aboard the ship, he is privately dismissed on several occasions due to his lack of discretion. Stevenson has Jim Hawkins observe that neither he nor the captain paid much regard to Mr. Trelawney's protestations, he was so loose a talker.

When the crew mutinies to steal the treasure, Trelawney, Livesey and their loyal crewmen surprise and overpower the few pirates who did not go ashore. They row ashore and move into an abandoned, fortified stockade. The pirates are defeated, the treasure is divided amongst Trelawney and his loyal men, and they return to England, leaving the surviving pirates marooned on the island.

The Squire is a well-traveled man and the best shot amongst the crew. He also shows effective leadership qualities and keeps a cool head throughout the adventure. Squire Trelawney may have been named for Edward Trelawney, Governor of Jamaica 1738-1752.