Thornton-in-Lonsdale is a village and civil parish in the District of Craven and ceremonial county of North Yorkshire in England. It is very close to the border with Cumbria and is north of Ingleton and south east of Kirkby Lonsdale, and has a population of 308. 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.
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 c720 acres /290ha 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 c6km long and its width tapered from c2km to c100m. However the majority of the parish, including Thornton and Burton-in-Lonsdale, was in Yorkshire.