Yes. A marriage in which one or both spouses is unbaptized is called a natural marriage.
The two things that make a marriage valid are consent and law.
The Church teaches that, unlike the Eucharist or confirmation, where the minister of the sacrament is a priest or bishop, the minister of marriage is the couple. The spouses mutually confer upon each other the marriage bond by expressing their consent. The essential requirement for a valid marriage is the exchange of consent to a life-long, faithful, life-giving relationship. Baptism is not required to be able to exchange this consent; thus, even two non-baptized persons can be validly married (though it is a natural rather than a sacramental marriage).
The second aspect is law. The Church has the authority to regulate marriage. At this time, the Church has laws that regulate only how Catholics attempt marriage; therefore, non-Catholics have only to have the right intentions (consent) to enter into marriage; they have no form to follow.