Alistair James Montagu Hay (born 1955) is an Australian botanist. He is a former director of the Royal Botanic Garden, Sydney. He is the heir presumptive to his older brother Charles Hay, 14th Marquess of Tweeddale (born 1947). Although entitled to the courtesy style of "Lord" as the younger son of a marquess, he does not use the style.

The standard author abbreviation A.Hay is used to indicate this person as the author when citing a botanical name.