In contract bridge, the Law of total tricks (abbreviated here as LoTT) is a guideline used to help determine how high to bid in a competitive auction. It is not really a law (because counterexamples are easy to find) but a method of hand evaluation which describes a relationship that seems to exist somewhat regularly. Written by Jean-René Vernes for French players in the 1950s as a rule of thumb, it was first described in English in 1966 International Bridge Academy Annals. It received more notice from appearing in The Bridge World in June 1969. In 1981 Dick Payne and Joe Amsbury, using their abbreviation TNT (Total Number of Tricks), wrote at length about it for British readers. Later, in the US, Marty Bergen and Larry Cohen popularized the approach, using their preferred abbreviation: 'the LAW' (all capitals).

It was prefigured in S. J. "Skid" Simon's 1945 book Why You Lose at Bridge in his aphorism "When in doubt, bid one more".