Isaac Weld JP FGSD MRIA (1774–1856) was an Irish topographical writer, explorer, and artist. He was a member of the Royal Dublin Society .
He was born on 15 March 1774 on Fleet Street, Dublin, Ireland. His name stems from his great grandfather Nathanael Weld's close friendship with Sir Isaac Newton, and as such both his grandfather and father were also named Isaac. His father was a close friend of Charles James Fox. His sister married George Ensor, and their half-brother was Charles Richard Weld, traveller and author of A Vacation Tour in the United States and Canada (London, 1855), which was dedicated to his brother, Isaac. He was sent to the school of Samuel Whyte at Grafton Street and from there to another private school Barbauld at Palgrave near the town of Diss in Norfolk. From Diss he proceeded to Norwich as a private pupil of Dr William Enfield. He left Norwich in 1793. He married Alexandra Hope in Edinburgh in 1802. He had a daughter Esther, named after his sister, born 7 January 1804. In later life, Weld spent much time in Italy and particularly Rome, where he developed a friendship with Antonio Canova.
In 1795 he sailed to Philadelphia from Dublin and spent two years travelling in the United States and Canada. He visited Monticello and Mount Vernon and met George Washington and Thomas Jefferson. He journeyed to the United States and Canada partly as an adventure and partly as research into suitable countries for the Irish to emigrate to: "any part of those territories might be looked forward to as an eligible and agreeable place of abode". He travelled on horseback, by coach and by canoe in Canada with local native guides. He returned in 1797 "without entertaining the slightest wish to revisit it." He found the Americans to be obsessed with material things and preferred Canada. His published Travels (1799) quickly went into three editions and was translated into French, German, Italian, and Dutch.