Jan van Os (23 February 1744 – 7 February 1808) was a Dutch painter and a member of the renowned Van Os family of artists.
Van Os was born in Middelharnis. He was taught by Aert Schouman in The Hague, where he would spend the rest of his life. In 1773, he recorded in the painters confraternity. In 1775, he married Susanna de La Croix, a deaf-mute pen portraitist.
Van Os is mostly known for his fruit and flower still life paintings, though he started his career painting seascapes. His floral still lifes were painted in the style of Jan van Huysum, with the flowers usually presented on a marble ledge against a green background.

He was the father of artists Pieter van Os, Maria Margaretha van Os, and Georgius Jacobus Johannes van Os and grandfather to the painter Pieter Frederik van Os.

Jan van Os

• 1744–1808
• Nationality: Dutch

Dutch family of painters active during the late 18th and 19th centuries, mainly in The Hague. Jan (1744–1808) was the founder. He and his daughter Maria Margaretha (1780–1862) and his son Georgius (1782–1861) specialized in painting flowers and fruits in the lavish detailed manner of Jan van Huysum. Another of Jan's sons, Pieter Gerardus (1776–1839), specialized in landscapes with cattle. His son and pupil, Pieter Frederik (1802–92), taught Mauve.