USS Halcyon II (SP-582) was a yacht acquired by the U.S. Navy during World War I.

She was outfitted as an armed patrol craft and stationed in Boston harbor in Massachusetts.

She spent much of the war patrolling the Massachusetts waterways for German submarines and, in 1919, was decommissioned after being damaged in a collision.

[citation needed] Halcyon II, a 161-ton steam yacht, was built by Charles Seabury Gas Engine & Power Co. of Morris Heights, Bronx, New York in 1907, and was purchased by the Navy in August 1917 from her owner, D. W. Flint of Providence, Rhode Island.

She performed this service until 4 June 1919 when she was rammed and seriously damaged by the steamer Bayou Teohe.