Lowther Augustus John Pennington, 3rd Baron Muncaster (14 December 1802 – 30 April 1838), styled Hon. Lowther Pennington from 1813 to 1818, was a landowner in northern England and an Irish peer. Lowther was the only son of General Lowther Pennington, who married the widow Esther Morrison in January 1802 while on half-pay. The general inherited the barony of Muncaster from his brother in 1813, and died in 1818, leaving Lowther to succeed him in the barony and estates.