Haw. Rev. Stat. § 574-1: Married persons; civil union partners.

Upon marriage or civil union, each of the parties to a marriage or partners in a civil union shall declare the middle and last names each will use as a married person or civil union partner. No person shall be required to change that person's middle or last name upon entering into a marriage or civil union. Parties to a marriage and partners in a civil union shall not be required to have the same middle or last name. Every person may adopt any middle or last name upon entering into a marriage or civil union.