Multi-instantons in large N Matrix Quantum Mechanics

We calculate the multi-instanton corrections to the ground state energy in large $N$ Matrix Quantum Mechanics. We find that they can be obtained, through a non-perturbative difference equation, from the multi-instanton series in conventional Quantum Mechanics, as determined by the exact WKB method. We test our results by verifying that the one-instanton correction controls the large order behavior of the $1/N$ expansion in the quartic potential and in the $c=1$ string.