The invention relates to a bleaching composition. In particular the invention provides a bleaching composition which comprises: (i) a bleaching agent, and (ii) as bleach catalyst, a polyoxometalate of Keggin, Dawson or Finke structure and having the general formula (II):(A')a'(Cox'Yy',Mm',Oo).cH2O wherein the or each A', which may be the same or different, is a cation; a' has a value such that (A')a' counters the anionic charge of (Cox', Yy', Mm', Oo); x' has a value of 0.25 to 4; the or each Y, which may be the same or different, represents P, Si or Co; y'is 1 or 2; o has a value of 34 to 68; the or each M, which may be the same or different, represents W, Mo, V, Nb or Ta; m' has a value of 9 to 18; and c has a value of between 0 and 84. The bleaching compositions according to the invention have good bleaching performance and can be used without a bleach activator, e.g. at low temperatures.