The development of standardised nomenclatures with associated databases containing reference sequences for alleles at polymorphic loci within the major histocompatibility complex (MHC) has been facilitated by the development of the immuno polymorphism database (IPD). Recently, included within IPD-MHC is information on allelic diversity within sheep species (IPD-MHC-OLA). Here, we present the first report of progress in populating the sheep IPD-MHC database with alleles at the class II MHC DRB1 locus. The sequence of 63 Ovar-DRB1 alleles within 24 allelic families is now held within the database, each meeting the minimum requirement of a complete second exon. These sequences are derived from a combination of genomic and cDNA-based approaches and represent the most extensive collection of validated alleles at the sheep DRB1 locus yet described. Although these 63 alleles probably represent only a fraction of the DRB1 allelic diversity in sheep species worldwide, we encourage the research community to use the official allelic nomenclature and to contribute allelic sequences to the database via its web-based submission tool. In time, the IPD-MHC-OLA resource will underpin population-based MHC genotyping studies and help to simplify meta-analyses of multi-source data from wild and domestic sheep populations.