Isaac Romilly (c.1710–1759) was an English businessman of Huguenot background, and a Fellow of the Royal Society.
He was the son of Etienne Romilly, a French migrant in London, and his wife Judith de Montsallier.
His brother Peter was father of Samuel Romilly.
He was in business with Samuel Fludyer and his brother Thomas.
[2] He died on 18 December 1759, aged 49, and was buried in St Bride's, Fleet Street.