  We study the relation between large N instantons and conventional instantons,
focusing on matrix models and topological strings. We show that the resurgent
properties of the perturbative series at fixed but arbitrary N, including the
replica limit N = 0, can be obtained from large N instantons. In the case of
topological strings, it has been conjectured that the resurgent structure
encoded by large N instantons is closely related to the spectrum of BPS states.
We give direct evidence for this connection in the case of Seiberg-Witten
theory and other topological string models, and we show in detail how the
resurgent properties at fixed N follow from the large N theory, and therefore
can be used to obtain information on BPS invariants.
