In the UK, a tied house (as opposed to a free house) is a pub that is owned or controlled by a brewery. The brewery usually acts as a landlord while the tenant takes responsibility for the actual running of the pub. (Ironically, this individual is traditionally known as "the pub landlord".)

In practice, the brewery will use its stronger bargaining position to influence several aspects of policy and management. Most importantly, the tenant will be required to sell the brewery's beer in exclusion of competing brands. This tactic is responsible for the ubiquity of tied houses.

At the start of the twentieth century British magistrates were using the licensing system to reduce the number of pubs across the country. The resulting shortage meant that breweries had to buy pubs or find themselves locked out of the market. By 1915 tied houses accounted for 95% of pub licences.

Since 1989 a law has granted tenants the right to stock "guest beers" which goes a little way towards helping independent breweries, however most beer is still produced by the large consolidated corporations.

Beer and Britannia, Peter Haydon, 2001
CAMRA website