MetOD1 (Methanogen output domain 1) is a protein domain that is found in euryarchaeal classes Methanobacteria and Methanomicrobia, either in stand-alone form or in combination with the Response_reg Pfam:PF00072 domain (Galperin et al., 2018, Phyletic distribution and lineage-specific domain architectures of archaeal two-component signal transduction systems). This domain is distantly related to the HNOB and V4R domains.