We deal with a class of equations driven by nonlocal, possibly degenerate, integro-differential operators of differentiability order s ∈ (0, 1) and summability growth p > 1, whose model is the fractional p-Laplacian with measurable coefficients. We state and prove several results for the corresponding weak supersolutions, as comparison principles, a priori bounds, lower semicontinuity, and many others. We then discuss the good definition of (s, p)-superharmonic functions, by also proving some related properties. We finally introduce the nonlocal counterpart of the celebrated Perron method in nonlinear Potential Theory.Keywords Quasilinear nonlocal operators · fractional Sobolev spaces · fractional Laplacian · nonlocal tail · Caccioppoli estimates · obstacle problem · comparison estimates · fractional superharmonic functions · the Perron Method