A prenuptial agreement (better known as a prenup), is a contract written and agreed upon by two people before getting married. A prenup is usually a list of assets prior to marriage, assigning joint items and private items during and after marriage (in the case of divorce).
While using a prenup seems a bit business-like, maybe moreso than the romantic nature of weddings and love, it can shield both people. If there are existing assets, or children from previous relationships, prenups might be worth exploring.