Nelson Doi, formally Nelson K. Doi (born January 1, 1922), was Lieutenant Governor of Hawaii from 1974 to 1978 in the administration of Governor of Hawaii George Ariyoshi. Doi is a member of the Hawaii Democratic Party.

Doi began his political career at the 1950 Hawaii State Constitutional Convention that drafted the first state laws for Hawaii that went into effect in 1959. He then served fourteen years in the Hawaii State Senate from 1955 to 1969. Upon leaving the Hawaii State Legislature, Doi was appointed to the Hawaii State Judiciary as a circuit court judge where he served for five years. It was from the court that Doi was chosen as the running mate for George Ariyoshi. Years earlier, Ariyoshi succeeded the governorship upon the death of John A. Burns. After his service with Ariyoshi, Doi was appointed to then-territorial High Court of the Marshall Islands. Upon his retirement from that court, Doi taught at various schools in Japan. He returned to Hawaii and settled on the Big Island of Hawaii where he helped build the North Hawaii Community Hospital.