monogamist

noun

One who has been married only once; one who believes that a person should not marry oftener than once —that is, that a widower or widow should not remarry.

noun

One who has but one (living and undivorced) wife, as opposed to a bigamist or a polygamist.

noun

One who practices or upholds monogamy.

noun

A person who practices monogamy

noun

someone who practices monogamy (one spouse at a time)