Mitochondrial import receptor subunit TOM40 homolog is a protein which in humans is encoded by the TOMM40 gene.

TOMM40 codes for a protein that is embedded into outer membranes of mitochondria and is required for the movement of proteins into mitochondria. More precisely, TOMM40 is the channel-forming subunit of the translocase of the outer membrane (TOM) complex, a translocase of the outer mitochondrial membrane that is essential for protein transport into the mitochondrion.

Certain alleles of this gene have been statistically associated with an increased risk of developing late-onset Alzheimer's disease. One study has found that TOMM40 risk alleles appear twice as often in people with Alzheimer's disease than those without it. Because TOMM40 is located on chromosome 19, and is closely adjacent to APOE, another gene known to be associated with Alzheimer's, another study has suggested that the statistically significant correlation of TOMM40 with Alzheimer's is due to linkage disequilibrium.