  Robert Harry Kraichnan {(1928-2008)} was one of the leaders in the theory of
turbulence for a span of about forty years (mid-fifties to mid-nineties). Among
his many contributions, he is perhaps best known for his work on the inverse
energy cascade (i.e. from small to large scales) for forced two-dimensional
turbulence. This is a review of Kraichnan's main scientific contributions.
