We study the stress tensor multiplet four-point function in the 6d maximally supersymmetric (2, 0) A(N-1) and D-N theories, which have no Lagrangian description, but in the large N limit are holographically dual to weakly coupled M-theory on AdS(7)x S-4 and AdS(7)x S-4/Z(2), respectively. We use the analytic bootstrap to compute the 1-loop correction to this holographic correlator coming from Witten diagrams with supergravity R and the first higher derivative correction R-4 vertices, which is the first 1-loop correction computed for a non-Lagrangian theory. We then take the flat space limit and find precise agreement with the corresponding terms in the 11d M-theory S-matrix, some of which we compute for the first time using two-particle unitarity cuts.
