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.
On 15 December 1828, Muncaster married Frances Catherine Ramsden (1806–1853), the daughter of Sir John Ramsden, 4th Baronet.
They had seven children: Muncaster died on 30 April 1838 at the Green Park Hotel in Piccadilly, and was buried on 15 May at Warter.