William Sadler II (c.1782 – 1839) was an Irish painter. He was a noted landscape painter.
William Sadler II was the son of the portrait painter and engraver William Sadler. Two of his sons became painters, the eldest being William Sadler III. (The numbers after each name are merely used to distinguish one from another).
Sadler lived at a number of different addresses before settling in Manders' Building, Ranelagh, where he died in December 1839.
Sadler, who grew up in Dublin, exhibited his paintings between 1809 and 1821 in the city. In 1828 and 1833 he exhibited at the Royal Hibernian Academy. Sadler also taught painting and one of his pupils was James Arthur O'Connor.
Sadler was greatly influenced by Dutch genre painting.