BBC Radio 4 is a British national radio station owned and operated by the BBC. The station replaced the BBC Home Service on 30 September 1967 and broadcasts a wide variety of spoken-word programmes from the BBC's headquarters at Broadcasting House, London. Since 2019, the station controller has been Mohit Bakaya. He replaced Gwyneth Williams, who had been the station controller since 2010.

Radio 4 is broadcast throughout the United Kingdom, the Isle of Man and the Channel Islands on FM, LW and DAB, and on BBC Sounds, it can also be received in the eastern counties of Ireland, northern France and Northern Europe. It is available internationally via the BBC.com website and app. It currently reaches over 9.2 million listeners, making it the UK's second most-popular radio station after BBC Radio 2.

BBC Radio 4 broadcasts news programmes such as Today, The World at One and PM heralded on air by the Greenwich Time Signal pips or the chimes of Big Ben. Radio 4 also broadcasts the Shipping Forecast, which is over 150 years old.

According to RAJAR, the station broadcasts to a weekly audience of 9.2 million with a listening share of 11.1% as of December 2023.

BBC Radio 4 broadcasts a wide variety of speech-related programming, including news, drama, comedy, science and history. Music is broadcast as in documentaries relating to various forms of both popular and classical music, and the long-running music-based Desert Island Discs. Sport is not part of the station's output, apart from during news bulletins, although between 1994 and 2023, the station's longwave frequency was used to broadcast ball-by-ball commentaries of most Test cricket matches played by England. Consequently, for around 70 days a year, listeners had to rely on FM broadcasts or DAB for mainstream Radio 4 broadcasts – the number relying solely on longwave was now a small minority. The cricket broadcasts took precedence over on-the-hour news bulletins, but not the Shipping Forecast, carried since Radio 4's move to longwave in 1978 because longwave can be received clearly at sea.

The station is available on FM in most of Great Britain, parts of Ireland and the north of France; LW throughout the UK and in parts of Northern Europe, and the Atlantic north of the Azores to about 20 degrees west; DAB; Digital TV including Freeview, Freesat, Sky and Virgin Media, and on the Internet. Freesat, Sky and Virgin have a separate channel for Radio 4 LW output in mono, in addition to the FM output.

BBC Radio 4 is the second-most-popular British domestic radio station by total hours, after Radio 2. It recorded its highest audience, of 11 million listeners, in May 2011, and was "UK Radio Station of the Year" at the 2003, 2004, 2008 and 2023 Radio Academy Awards. It also won a Peabody Award in 2002 for File on 4: Export Controls. Costing £87 million (2024/5), it is the BBC's most expensive national radio network. There is no comparable British commercial network: Channel 4 abandoned plans to launch its own speech-based digital radio station in October 2008 as part of a £100m cost-cutting review.

The longwave signal is part of the Royal Navy's system of letters of last resort. In the event of a suspected catastrophic attack on Britain, submarine captains, in addition to other checks, check for a broadcast signal from Radio 4 on 198 kHz longwave to verify the annihilation of organised society in the United Kingdom.^{[failed verification]}