果寡糖（Fructooligosaccharides，通常简写作FOS，亦作oligofructose或oligofructan）是一种天然的寡糖，亦有作代糖使用。一般市面上采用果寡糖作糖浆，其甜度约为砂糖的30~50%左右。能有助双叉杆菌及嗜酸杆菌等肠内益菌的繁殖，抑制坏细菌的增生，帮助排便，保持肠道健康。果寡糖存在于天然，其商品化开始于1980年代，由于当时的人期望透过控制饮食中摄取的热量来控制体重。

Fructooligosaccharides (FOS) also sometimes called oligofructose or oligofructan, are oligosaccharide fructans, used as an alternative sweetener. FOS exhibits sweetness levels between 30 and 50 percent of sugar in commercially prepared syrups. It occurs naturally, and its commercial use emerged in the 1980s in response to consumer demand for healthier and calorie-reduced foods.