First release of MammalMethylClock R package Epigenetic clocks are prediction methods that relate cytosine methylation levels at specific genomic sites to chronological age, in a given species or set of species. Defined as multivariate regression models, these DNA methylation-based biomarkers have gained prominence in species conservation efforts and preclinical studies. Once built, these models predict an individual's age from their tissue sample's cytosine methylation profile, with great potential for aging research, disease risk prediction, and gauging intervention impacts. Through the collaborative efforts of our leadership of the Mammalian Methylation Consortium, we describe epigenetic clocks for numerous mammalian species. Our R package includes the utility for implementing these pre-existing mammalian clocks. We present this dedicated R package called MammalMethylClock, designed for the construction, assessment, and application of epigenetic clocks.