ADT Inc., formerly The ADT Corporation, is an American company that provides residential, small and large business electronic security, fire protection, and other related alarm monitoring services throughout the United States. The corporate head office is located in Boca Raton, Florida. In February 2016, the company was acquired by Apollo Global Management for $6.9 billion in a leveraged buyout.

In early 1987, the firm Hawley Goodall, owned by Lord Ashcroft, bought the Indianapolis-based Crime Control Inc., the fourth-largest company in the U.S. security market, for $50 million. Later in the year, it bought ADT and moved to Bermuda. This purchase transformed Hawley into the leading security services business in the United States and resulted in the majority of its revenues coming from the North American market. As a result of the acquisition, Hawley changed its name to ADT Limited and decided to refocus its business around security services. At the end of 1987, the company sold its North American–based facility services business to Denmark’s ISS A/S.

In 1997, ADT was purchased by Tyco International in a reverse takeover.

The company is registered in the UK as ADT Fire & Security PLC