Steak sauce (in North America) — brown sauce (in the British Isles) — is a generic term for a dark brown sauce commonly served as a condiment for meat.
The two terms are similar but not identical. In the United States, as its name implies, steak sauce is predominantly associated with beef, while elsewhere brown sauce is often used on a variety of foods.
The most well known brands are A1 Steak Sauce in the United States, and HP Sauce in the United Kingdom. In the UK brown sauce is also popular on bacon sandwiches and pie and mash.