The Occupiers' Liability Act 1957 (5 & 6 Eliz. 2. c. 31) is an act of the Parliament of the United Kingdom that covers occupiers' liability. The result of the Third Report of the Law Reform Committee, the act was introduced to Parliament as the Occupiers' Liability Bill and granted royal assent on 6 June 1957, coming into force on 1 January 1958.

The act unified several classes of visitors to property and the duty of care owed to them by the occupier, as well as codifying elements of the common law relating to this duty of care. It also covered the duty owed to parties to a contract entering the property and ways of excluding the liability for visitors. The act introduced an element of liability for landlords who failed to maintain their properties and were as a result responsible for the injury of a non-tenant, something counter to the previous common law rule in English law. The act is still valid law, and forms much of the law relating to occupiers' liability in English law along with the Occupiers' Liability Act 1984.

Prior to 1957, visitors to a property were classified in different ways, and this classification determined the duty of care an owner or tenant had to them. These were "contractors" such as hotel guests (the highest level of duty: a duty to ensure that the premises were fit for the purposes of the contract), "invitees", such as a customer in a shop (owed a less onerous duty: a duty to take reasonable care to prevent damage from an unusual danger), "licensees", such as a friend invited to a party (a less onerous duty again: a duty to warn of any concealed danger or trap of which the occupier knew) and "uninvited persons" such as trespassers (who were owed no duty of care, except to refrain from deliberately or recklessly causing them harm).

The Third Report of the Law Reform Committee recommended changing this system, and the Occupiers' Liability Bill was given its second reading on 6 March 1957 by Sir Harry Hylton-Foster, the Solicitor General, and royal assent on 6 June 1957.

The Act first identifies the occupier. Section 1(2) identifies the occupier as the person occupying or in control of the premises, not necessarily the owner, with the underlying premise being that the person liable should be the person most likely to have been able to prevent the harm; the person occupying the premises, not necessarily the owner of those premises. The Act does not define occupier, but provides that the person to be treated as the occupier is the person who would be considered an occupier under common law rules. In Wheat v E Lacon & Co Ltd [1966] 1 All ER 582 it was established that more than one person can be an occupier. In Harris v Birkenhead Corporation [1976] it was held that it was possible to be an occupier without having physical possession of the house if the "occupier" has legal control of the property. Section 1(3) extends the standards set by the Act not only to land but to any fixed or movable structure, which includes ships and aircraft.

The Act next establishes a uniform duty towards all lawful visitors, thus abolishing the distinction between contractors, invitees and licensees. Section 2 provides that the occupier has a "common duty of care" to all lawful visitors, although it keeps the low duty of care towards unlawful visitors such as trespassers. The new duty is defined as "a duty to take such care as in all the circumstances of the case is reasonable to see that the visitor will be reasonably safe in using the premises for the purposes for which he is invited or permitted by the occupier to be there". The Act allows the occupier to set limits on where the visitor is allowed to go or how long they are allowed to be there, an extension of the common law judgment made by Scrutton LJ in The Calgarth [1927], when he said that "when you invite a person into your house to use the staircase, you do not invite him to slide down the bannisters, you invite him to use the staircase in the ordinary way in which it is used".

Exceptions are made for children and a person "in the exercise of his calling" (a professional person or somebody exercising a trade or skill). With children, occupiers must "be prepared for children to be less careful than adults"; a warning notice, for example, would normally be good enough to alert adults to a potential danger, but not to alert children. This is another extension of a common law principle; in Glasgow Corporation v Taylor [1922] 1 AC 44, a seven-year-old child died after eating poisonous berries from a bush in a park. The berries, which looked like cherries or blackcurrants, were found by the House of Lords to constitute an "allurement" to the child, who found Glasgow Corporation, which owned the park, liable. However, the situation is different if the child has a guardian with him, who one would expect to appreciate any obvious dangers, as in Phipps v Rochester Corporation [1955] 1 QB 450. This was essentially the same as the existing common law; indeed, "It is doubtful whether the Act alters the law at all on this point".

An occupier has a less onerous duty towards a person "in the exercise of his calling", such as a professional or somebody exercising a trade. Section 2(3)(b) of the Act provides that such a person "will appreciate and guard against any special risks ordinarily incidental to [his calling], so far as the occupier leaves him free to do so". In Roles v Nathan 2 All ER 908 a pair of chimney sweeps were called to clean the flues of a boiler. The engineer warned them about the risk of carbon monoxide poisoning if the chimney sweeps cleaned the flues with the fires still lit, but they disregarded his warning and continued until they were overwhelmed by carbon monoxide and died. The Court of Appeal held that the occupier was not liable, because the chimney sweeps had been warned and a householder who calls in a specialist to deal with defective property can reasonably expect the specialist to guard against any obvious dangers.