Lydia was a US merchant ship that sailed on maritime fur trading ventures in the early 1800s. In December 1813 it was sold to the Russian–American Company and renamed Il'mena, also spelled Ilmena and Il'men' (Russian: Ильмена). As both Lydia and Il'mena it was involved in notable events. Today it is best known for its role in an 1814 massacre of the Nicoleño natives of San Nicolas Island, which ultimately resulted in one Nicoleño woman, known as Juana Maria, living alone on the island for many years. These events became the basis for Scott O'Dell's 1960 children's novel Island of the Blue Dolphins and the 1964 film adaptation Island of the Blue Dolphins.

The vessel was a brig built in the East Indies of teak. In April 1809 Lydia, under captain Thomas Brown, left Boston for the Pacific Northwest Coast. In 1810 Brown rescued the Russian survivors of Sv. Nikolai ("St. Nicholas"), which had wrecked on the Olympic Peninsula in November 1808. They were taken aboard Lydia and brought to Sitka, the capital of Russian America. In October 1811 Thomas Brown exchanged commands with James Bennett of Derby. In late 1813 Bennett took Lydia to Sitka where the vessel was sold to the Russian–American Company (RAC) and renamed Il'mena.

As an RAC vessel Il'mena, under captain William Wadsworth, brought Aleuts with their kayaks and baidarkas to California to hunt sea otters along the coast of California, in 1814. During this time an altercation with the Nicoleño of San Nicolas Island resulted in a massacre of the Nicoleño. In addition some of the RAC employees were captured by the authorities of Spanish California, who considered their activity poaching.

From September 1815 to April 1816 Il'mena was laid up at Bodega Bay for repairs. The vessel was taken to the Hawaiian Islands in 1816, where it became involved in the Schäffer affair before leaving in June 1817 under captain George Young. By late June 1817 Il’mena was back at Sitka. In 1820 Il'mena wrecked at Point Arena on the coast of California. All the people and cargo on board were saved and taken to nearby Fort Ross.

Lydia was a brig built in the East Indies of teak. By 1804 it was owned by Theodore Lyman and Associates of Boston. By 1809 Lyman was joined in ownership by James & Thomas Handasyd Perkins (J. & T.H. Perkins).

Sources differ over the size of the vessel. Some sources say it was 200 tons, while others say 50 tons.

In April 1809 the brig was sent from Boston on a maritime fur trade voyage to the Pacific Northwest, under Captain Thomas Brown. Lydia spent 1810 to 1813 cruising the Northwest Coast, between about the Columbia River and Sitka Sound, trading with the indigenous peoples of the Pacific Northwest Coast for sea otter furs, which commanded a high price in China.

In 1810 Captain Brown rescued the Russian survivors of Sv. Nikolai ("St. Nicholas"), which had wrecked near Rialto Beach on the Olympic Peninsula on 1 November 1808. The survivors, led by Timofei Nikitich Tarakanov, lived with the Hoh and Makah in a servile way until rescued by Brown. One of the Russian survivors from Nikolai was on board Lydia, having been sold as a slave to the south and acquired by Captain Brown on the Columbia River. Later Brown visited the Makah village at Neah Bay where on 22 May he arranged to purchase the Russians enslaved there. They were taken aboard Lydia and brought to Sitka, the capital of Russian America.