Domestic partner adoption describes an adoption where one partner adopts the other partner’s child, so that both become the child’s legal parents. In UK and Irish practice this is more commonly termed step‑parent adoption, second‑parent adoption or adoption by a civil partner or cohabitant, rather than “domestic partner adoption”, which is not a defined statutory term.In England and Wales, and Scotland, adoption by a partner is governed mainly by the Adoption and Children Act 2002 and the Adoption and Children (Scotland) Act 2007, which allow applications by spouses, civil partners and certain long‑term cohabitants. Northern Ireland has similar provision under the Adoption (Northern Ireland) Order 1987 as amended, now allowing unmarried and same‑sex couples to adopt. In Ireland, the Adoption Act 2010 (as amended, including by the Adoption (Amendment) Act 2017) permits adoption by spouses, civil partners and qualifying cohabitants.Key features include: extinguishing (with limited exceptions) the legal status of the other birth parent; transferring parental responsibility/parental rights and responsibilities; rigorous welfare‑based assessment; and full legal equality of the adoptive parent with any existing legal parent. The term is used in practice to distinguish these intra‑family adoptions from stranger or intercountry adoptions.