John Wilder Tukey was a scientific generalist, a chemist by undergraduate training, a topologist by graduate training, an environmentalist by his work on Federal Government panels, a consultant to US corporations, a data analyst who revolutionized signal processing in the 1960s, and a statistician who initiated grand programmes whose effects on statistical practice are as much cultural as they are specific. He had a prodigious knowledge of the physical sciences, legendary calculating skills, an unusually sharp and creative mind, and enormous energy. He invented neologisms at every opportunity, among which the best known are ‘bit’ for binary digit, and ‘software’ by contrast with hardware, both products of his long association with Bell Telephone Labs. Among his legacies are the fast Fourier transformation, one degree of freedom for non-additivity, statistical allowances for multiple comparisons, various contributions to exploratory data analysis and graphical presentation of data, and the jackknife as a general method for variance estimation. He popularized spectrum analysis as a way of studying stationary time series, he promoted exploratory data analysis at a time when the subject was not academically respectable, and he initiated a crusade for robust or outlier-resistant methods in statistical computation. He was for many years a scientific adviser to Presidents Eisenhower, Kennedy, Johnson and Nixon. A 1965 report he wrote was the impetus leading to Congressional action that created the Environmental Protection Agency, and a later 1976 report (4)* confirmed the threat of halocarbons to stratospheric ozone. His work for the State Department on the Nuclear Weapons Test Ban Treaty led him to develop data-analytic tools to distinguish explosions from earthquakes. Evidence of his influence can be seen in a wide areas of science and technology, from oceanography to seismology, from topology to sampling and statistical graphics. Among many honours, he was awarded the S.S. Wilks award of the American Statistical Association in 1965, the Medal of Honour of the Institute of Electronic and Electrical Engineers in 1982, and the US National Medal of Science in 1973.