The August 2011 Higgs mass prediction was based on an ongoing six year project studying M-theory compactified on a manifold of G2 holonomy, with significant contributions from Jing Shao, Eric Kuflik, and others, and particularly co-led by Bobby Acharya and Piyush Kumar. The M-theory results include: stabilization of all moduli in a de Sitter vacuum; gauge coupling unification; derivation of TeV scale physics (solving the hierarchy problem); the derivation that generically scalar masses are equal to the gravitino mass which is larger than about 30 TeV; derivation of the Higgs mechanism via radiative electroweak symmetry breaking; absence of the flavor and CP problems, and the accommodation of string axions. tan beta and the mu parameter are part of the theory and are approximately calculated; as a result, the little hierarchy problem is greatly reduced. This paper summarizes the results relevant to the Higgs mass prediction. A recent review describes the program more broadly. Some of the results such as the scalar masses being equal to the gravitino mass and larger than about 30 TeV, derived early in the program, hold generically for compactified string theories as well as for compactified M-theory, while some other results may or may not. If the world is described by M-theory compactified on a G2 manifold and has a Higgs mechanism (so it could be our world) then the Higgs mass was predicted to be 126 +/- 2 GeV before the measurement. The derivation has some assumptions not related to the Higgs mass, but involves no free parameters.