| Alexey Ivanovich Nagayev | |
| Native Name: | Алексей Иванович Нагаев |
| Birth Date: | 17 March 1704 |
| Death Date: | 8 January 1781 |
| Birth Place: | Sertyakino, Tsardom of Russia |
| Death Place: | Saint Petersburg, Russian Empire |
| Allegiance: | |
| Rank: | Admiral |
| Commands: | 32-gun frigates "Chevalier" and "Mercurius" 66-gun ship "Fridemaker" Russian Hydrographic Service |
| Awards: | Order of Saint Alexander Nevsky Order of Saint Anna |
Alexey Ivanovich Nagayev (Russian: Алексей Иванович Нагаев, March 17, 1704, Sertyakino - January 8, 1781, Saint Petersburg) was a Russian hydrographer, cartographer and an admiral.
Born in a family of the lesser nobility, he graduated from the Saint Petersburg Naval Academy and later found employment there. During the Seven Years' War Nagayev headed the hydrographic expedition to the Prussian shores. He also compiled the first atlases of the Bering Sea and Baltic Sea, which were published in 1752. Despite the absence of a meridian grid, Nagayev's maps were used for a further fifty years. In 1764-65 Nagayev became the supreme commander of the Kronstadt port. He was promoted to the rank of admiral in 1769.
A bay in the Okhotsk Sea is named after him.