Mitochondria have been long known as "gatekeepers of life and death". Indeed, these dynamic organelles are the master coordinators of energy metabolism, being responsible for the generation of the majority of cellular ATP. Notably, mitochondria are also one of the primary producers of intracellular reactive oxygen species which are the main inducer of oxidative damage. Neurons, as metabolically active cells with high energy demands, are predominantly dependent on mitochondrial function, as reflected by the observation that mitochondrial defects are key features of chronic neurodegenerative diseases. Indeed, morphologic, biochemical and molecular genetic studies posit that mitochondria constitute a convergence point for neurodegeneration. Moreover, recent findings convey that neurons are particularly reliant on the dynamic properties of mitochondria, further emphasizing the critical role of mitochondria in neuronal functions. This chapter highlights how mitochondrial pathobiology might contribute to neurodegeneration in Alzheimer's, Parkinson's and Huntington's diseases.