Althorp (/ˈɔːlθɔːp/ or /ˈɔːltrəp/) is a Grade I listed stately home, estate and small civil parish in Daventry District, Northamptonshire, England of about 13,000 acres (5,300 ha). By road it is about 6 miles (9.7 km) northwest of the county town of Northampton and about 75 miles (121 km) northwest of central London. It has been held by the prominent aristocratic Spencer family for more than 500 years, and has been owned by Charles Spencer, 9th Earl Spencer since 1992. It was also the home of his sister, Lady Diana Spencer later Princess of Wales, before her marriage to Charles, Prince of Wales.
Althorp is mentioned as a small hamlet in the Domesday Book as "Olletorp", and by 1377 it had become a village with a population of more than fifty people. By 1505 there were no longer any tenants living there, and in 1508, John Spencer purchased Althorp estate with the funds generated from his family's sheep-rearing business. Althorp became one of the prominent stately homes in England. The mansion dates to 1688, replacing an earlier house that was once visited by Charles I. The Spencer family amassed an extensive art collection and other valuable household items. During the 18th century, the house became a major cultural hub in England, and parties were regularly held, attracting many prominent members of Great Britain's ruling class. George John, 2nd Earl Spencer, who owned Althorp between 1783 and his death in 1834, developed one of the largest private libraries in Europe at the house, which grew to over 100,000 books by the 1830s. After falling on hard times, John Spencer, 5th Earl Spencer, known as the Red Earl, in 1892 sold much of the collection to Enriqueta Rylands, who was building the University of Manchester Library. Many of Althorp's furnishings were sold off during the twentieth century, and between 1975 and 1992 alone approximately 20% of the contents were auctioned.