幕斯（法文：Mousse，又译抹士、慕斯和慕丝）是由鸡蛋与忌廉（古典的作法不使用忌廉，仅使用蛋黄、蛋白、砂糖、朱古力或其它香料）所制作的乳脂状甜品，主要为朱古力和水果的组合。蛋白在与其它材料混合之前会先搅打至发泡，产生轻盈的口感与芳醇的风味。

1960年代从法国餐厅中出现，之后朱古力幕斯成了美国与英国的家常料理。美国中部地区也有类似抹士的甜点，称为「Whip」。 除此之外也有与抹很相似的巴伐洛亚甜品 ，但从材料到制作的方法都不大相同。

作为前菜的抹士，可能煲的原只鸡蛋、鱼或肝脏作材料。

A mousse (French 'foam' /ˈmuːs/) is a prepared food that incorporates air bubbles to give it a light and airy texture. It can range from light and fluffy to creamy and thick, depending on preparation techniques. A mousse may be sweet or savory. Dessert mousses are typically made with whipped egg whites or whipped cream, flavored with chocolate, coffee, caramel, puréed fruits or various herbs and spices, such as mint or vanilla. Sweetened mousse is served as a dessert, or used as an airy cake filling. It is sometimes stabilized with gelatin. Savory mousse may be flavored with hard boiled egg, herbs, fish or liver.