Isaac Townsend (c.1685 – 21 November 1765) was an admiral in the British Royal Navy and a Member of Parliament. A post-Captain from 1720, Townsend commanded various ships. As captain of HMS Shrewsbury he took part in the expedition against Cartagena in 1741. He was promoted to Rear Admiral in 1744, Vice Admiral in 1746 and Admiral in 1747. He was also an Elder Brother of Trinity House. He was elected a Fellow of the Royal Society in February 1750. Townsend married Elizabeth Larcum, daughter of William Larcum, a surgeon, and they had one son and one daughter. He died in 1765.