As a crucial component to preventing sexual boredom and maintaining sexual and relationship satisfaction, sexual novelty is a relational characteristic that warrants considerable empirical attention; however, there is relatively little research on the role that sexual novelty plays in long-term, committed relationships. As such, we developed a brief, reliable measure of sexual novelty to stimulate additional research in this area. Participants consisted of 518 U.S. citizens in committed relationships of 6 months or longer who were recruited online through Amazon’s Mechanical Turk to complete surveys assessing “sexual relationships.” Across two samples, the unidimensional Sexual Novelty Scale (SNS) demonstrated high internal consistency and test-retest reliability, as well as convergent and divergent validity. Our results indicate that the 5-item Sexual Novelty Scale is a brief, reliable, and valid measure of the extent to which partners in committed romantic relationships engage in sexually novel behaviour.