James Derrick Slater (13 March 1929 – 18 November 2015) was a British accountant, investor and business writer. Slater rose to prominence in the 1970s as a businessman and financier, who was the founding Chairman of Slater Walker, an investment bank and conglomerate which collapsed in the secondary banking crisis of 1973–75.

Born in 1929 in Heswall – at that time in Cheshire – Slater qualified as a chartered accountant aged 24, and joined the Dohm Group. Quickly promoted, he became a general manager, reorganising all the company's small industrial holdings into one company within the group. After leaving Dohm, he was appointed secretary and chief accountant of Park Royal Vehicles, a wholly owned subsidiary of ACV Group. He was then made commercial director of its subsidiary AEC. After Leyland Motors took over ACV, Slater was later promoted to deputy sales director under Donald Stokes.

Whilst working for AEC as a director, Slater fell ill and during his recovery became interested in investing, and developed a system for picking stocks which would much later form the basis of his book The Zulu Principle (1992). He then approached his friend Nigel Lawson, at that time the City Editor of The Sunday Telegraph, and was hired to write an investment column under the pseudonym 'Capitalist'. Over the following two years, Capitalist's ghost portfolio appreciated by 68.9%, against the London Stock Market's average of 3.6%.

In 1964, Slater acquired control of H Lotery & Co Ltd, a £1.5m public company; he and his business partner Peter Walker – a Conservative MP – renamed it Slater Walker Securities. The company performed what became known as corporate raids on public, mainly industrial, companies, in which Slater would sell off under-performing assets to improve efficiency. Slater commented, "we are money makers, not thing makers".

This saw the company growing into a group capitalized at over £200 million, through which Slater became a friend and business associate of James Goldsmith. Slater Walker then changed strategy, from a corporate-conglomerate into what eventually was recognised as an unauthorised and unlicensed international investment bank, through gradual disposal of its industrial interests. This has led to Slater being revered in some circles as a "merger lord", but criticised in others as an "asset stripper".

During the secondary banking crisis in 1975, Slater Walker faced financial difficulties and received support from the Bank of England. Slater resigned as chairman in October 1975 due to extradition attempts from the government of Singapore for the alleged misuse of more than £4 million of company funds in share deals. The Singapore government's attempt to extradite Slater (in which it was represented by Derry Irvine, assisted by Tony Blair and Cherie Booth) was dismissed by the Chief Metropolitan Magistrate at Horseferry Road Magistrates' Court in 1977. In separate proceedings, following the takeover of the company by the Bank of England, a prosecution was brought against Slater by the Department of Trade alleging 15 counts of offences under the Companies Act. Slater was found guilty of the Companies Act offences and fined £15 per count. However, the court accepted that the offences were purely technical, that Slater had not acted dishonestly and that there was no question of him having made any personal gain through committing them.

After the collapse of Slater Walker, and while being technically but not legally bankrupt, Slater invested his residual funds and repaid his personal creditors within a few years, with interest.

In 1976, Slater had formed a 50:50 venture with Tiny Rowland's Lonrho Group, to buy-up undervalued blocks of flats in London. At its peak, the company owned and managed over 1,500 flats. This business model led Slater to form Salar Properties, which through time share leasing of salmon fishing rights on seven of Scotland's rivers, including the Lower Redgorton beat on the River Tay, by the 1980s had become the largest Scottish fishing venture.