Thornton in Lonsdale is a village and civil parish in the Craven District and ceremonial county of North Yorkshire in England. It is very close to the border with Cumbria and Lancashire and is 1 mile (1.6 km) north of Ingleton and 5 miles (8.0 km) south-east of Kirkby Lonsdale, and has a population of 308, falling to 288 at the 2011 Census. Its main claims to fame are the Marton Arms pub and St Oswald's Church, Sir Arthur Conan Doyle married his first wife at this church in 1885 and held his reception at The Marton Arms before setting off to Ireland on honeymoon. Doyle's mother resided at nearby Masongill from 1882 to 1917.

In 1086 the Domesday Book listed on folio 301v under Craven Torntun & in Borch, Orm vi curactes ad geld. – that is in Thornton in Lonsdale with Burrow-with-Burrow Orm has circa 720 acres of plough-land to be taxed. This manor belonged to Orm, one of the family of Norse Noblemen who held the most land in Northern England. All estates would also include grazing land but since only arable land was tallied their total area can only be induced.

Because the parish of Thornton in Lonsdale was in the Lonsdale Hundred, a region more ancient than the county of Lancashire, it lay across two counties. A strip down the left side of the parish including Ireby was in Lancashire. The Lancashire area was about 3.7 miles (6 km) long and its width tapered from about 1.2 miles (2 km) to about 330 feet (100 m). However the majority of the parish, including Thornton and Burton in Lonsdale, was in Yorkshire.

• St Oswald's Church, Thornton in Lonsdale