  We report the observation of the decay mode B -> phi phi K based on an
analysis of 78 fb^{-1} of data collected with the Belle detector at KEKB. This
is the first example of a b -> s sbar s sbar s transition. The branching
fraction for this decay is measured to be B(B^{+-} -> phi phi K^{+-}) = (2.6
^{+1.1}_{-0.9} +- 0.3) x 10^{-6} for a phi phi invariant mass below 2.85
GeV/c^2. Results for other related charmonium decay modes are also reported.
