Sterling Drug was an American global pharmaceutical company, also known as Sterling Winthrop, Inc. in its last years (after the merger with Winthrop-Stearns Inc. which itself resulted from the merger of Winthrop Chemical Company Inc. and Frederick Stearns & Company). It was formerly known as Sterling Winthrop Pharmaceuticals, whose primary product lines included diagnostic imaging agents, hormonal products, cardiovascular products, analgesics, antihistamines and muscle relaxants.

Chemical compounds produced by this company were often known by their manufacturing code which consisted of the abbreviation WIN (for Winthrop) followed by a number. For example, WIN 18,320 was nalidixic acid, the first quinolone antibiotic.