The Naval Defence Act 1889 was an act of the Parliament of the United Kingdom. It received royal assent on 31 May 1889 and formally adopted the "two-power standard" and increased the United Kingdom's naval strength. The standard called for the Royal Navy to maintain a number of battleships at least equal to the combined strength of the next two largest navies in the world, which then were France and Russia. An extra £20 million over the following four years were provided for ten new battleships, thirty-eight new cruisers, eighteen new torpedo boats and four new fast gunboats. The two-power standard was maintained until disarmament began during the interwar period.