Emanuel Mendes da Costa (5 June 1717 – 31 May 1791)[a] was an English botanist, naturalist, philosopher, and collector of valuable notes and of manuscripts, and of anecdotes of the literati.

A brother became a wealthy businessman but Emanuel worked in the office of a notary and qualified from the Scriveners' Company in 1762 but had taken an interest in natural history from around 1736.

Da Costa was elected one of the first Jewish Fellows of the Royal Society of London in 1747, sponsored by Martin Folkes, the Duke of Montagu, and others.

In 1750 da Costa married a cousin, Leah, whose brother Abraham del Prado was a wealthy contractor for the English army, supplying food.

In 1763 the death of Francis Hauksbee, who had served for forty years as clerk to the Royal Society, led to an opening that he bid for by enlisting the votes and endorsements from his friends and correspondents.