.cx is the country code top-level domain (TLD) for Christmas Island. It is administered by Christmas Island Internet Administration (CIIA), a community-owned non-profit company which also provides Internet service to the island's residents.

The TLD was formerly administered by Planet Three Limited, a company with offices in the United Kingdom and Australia, which went bankrupt and ceased operations, voluntarily transferring management to CIIA (called Dot CX Limited at the time). The local (shire) government of Christmas Island endorsed the transfer, but the Commonwealth of Australia (which has international authority over Christmas Island as an external territory) did not immediately approve it. Australia has since published a Memorandum of Understanding which recognizes CIIA as the legitimate manager of .cx.