Mitochondrial DNA (mtDNA or mDNA) is the DNA in mitochondria. It is inherited only from mothers, though there are a few rare exceptions.

Mitochondria are cellular organelles in eukaryotic cells. They convert chemical energy from food into a form that cells can use, adenosine triphosphate (ATP). Mitochondrial DNA is only a small part of the DNA in a eukaryotic cell. Most of the DNA is in the cell nucleus on chromosomes. In plants, the chloroplasts have DNA as well.