Regent's Park (officially The Regent's Park) is one of the Royal Parks of London. It occupies 410 acres (170 ha) in north-west Inner London, administratively split between the City of Westminster and the Borough of Camden (and historically between Marylebone and Saint Pancras parishes). In addition to its large central parkland and ornamental lake, it contains various structures and organizations both public and private, generally on its periphery, including Regent's University and London Zoo.

What is now Regent's Park came into possession of the Crown upon the dissolution of the monasteries in the 1500s, and was used for hunting and tenant farming. In the 1810s, the Prince Regent proposed turning it into a pleasure garden. The park was designed by John Nash and James and Decimus Burton. Its construction was financed privately by James Burton after the Crown Estate rescinded its pledge to do so, and included development on the periphery of townhouses and expensive terrace dwellings. The park is Grade I listed on the Register of Historic Parks and Gardens.

The park has an outer ring road called the Outer Circle (4.45 km) and an inner ring road called the Inner Circle (1 km), which surrounds the most carefully tended section of the park, Queen Mary's Gardens. Apart from two link roads between these two, the park is reserved for pedestrians (with the exception of The Broad Walk between Chester Road and the Outer Circle, which is a shared use path). The south, east and most of the west side of the park are lined with elegant white stucco terraces of houses designed by John Nash and Decimus Burton. Running through the northern end of the park is Regent's Canal, which connects the Grand Union Canal to London's historic docks. The 166 ha (410-acre) park is mainly open parkland with a wide range of facilities and amenities, including gardens; a lake with a heronry, waterfowl and a boating area; sports pitches; and children's playgrounds. The northern side of the park is the home of London Zoo and the headquarters of the Zoological Society of London. There are several public gardens with flowers and specimen plants, including Queen Mary's Gardens in the Inner Circle, in which the Open Air Theatre stands; the formal Italian Gardens and adjacent informal English Gardens in the south-east corner of the park; and the gardens of St John's Lodge. Winfield House, the official residence of the U.S. Ambassador to the United Kingdom, stands in private grounds in the western section of the park, near the capital's first large mosque.

South of the Inner Circle is dominated by Regent's University London, home of the European Business School London, Regent's American College London (RACL) and Webster Graduate School among others.

Abutting the northern side of Regent's Park is Primrose Hill, another park which, with a height of 64 m (210 ft), has a clear view of central London to the south-east, as well as Belsize Park and Hampstead to the north. Primrose Hill is also the name given to the immediately surrounding district.

The public areas of Regent's Park are managed by The Royal Parks, a charity. The Crown Estate Paving Commission is responsible for managing certain aspects of the built environment of Regent's Park. The park lies within the boundaries of the City of Westminster and the London Borough of Camden, but those authorities have only peripheral input to the management of the park. The Crown Estate owns the freehold of Regent's Park.

In the Middle Ages the land was part of the manor of Tyburn, acquired by Barking Abbey. The 1530s Dissolution of the Monasteries meant Henry VIII appropriated it, under that statutory forfeiture with minor compensation scheme. It has been state property since. It was set aside as a hunting and forestry park, Marylebone Park, from that Dissolution until 1649 after which it was let as small-holdings for hay and dairy produce.

Although the park was initially the idea of the Prince Regent, and was named for him, James Burton, the pre-eminent London property developer, was responsible for the social and financial patronage of the majority of John Nash's London designs, and for their construction. Architectural scholar Guy Williams has written, "John Nash relied on James Burton for moral and financial support in his great enterprises. Decimus had showed precocious talent as a draughtsman and as an exponent of the classical style... John Nash needed the son's aid, as well as the father's". Subsequent to the Crown Estate's refusal to finance them, James Burton agreed to personally finance the construction projects of John Nash at Regent's Park, which he had already been commissioned to construct: consequently, in 1816, Burton purchased many of the leases of the proposed terraces around, and proposed villas within Regent's Park, and, in 1817, Burton purchased the leases of five of the largest blocks on Regent Street. The first property to be constructed in or around Regent's Park by Burton was his own mansion: The Holme, which was designed by his son, Decimus Burton, and completed in 1818. Burton's extensive financial involvement "effectively guaranteed the success of the project". In return, Nash agreed to promote the career of Decimus Burton. Such were James Burton's contributions to the project that the Commissioners of Woods described James, not Nash, as "the architect of Regent's Park".