Title An Atlas of Abstract Regular Polytopes for Small Groups Author Dimitri Leemans and Laurence Vauthier Reference Aequationes Math. 72(2006, nr. 3, 313-320. Abstract For each almost simple group G such that S <= G <= Aut(S) and S is a simple group of order less than 900,000 listed in the Atlas of Finite Groups, we give, up to isomorphism, the number of abstract regular polytopes on which G acts regularly. The results have been obtained using a series of Magma programs. All these polytopes are made available on the first author's website, at http://cso.ulb.ac.be/~dleemans/polytopes/