黄藻（Xanthophyceae）是一类属于不等鞭毛类的藻类生物。体类型为单细胞、群体、多核管状或丝状体。细胞壁含多量果胶质。运动的个体和动孢子具有2条不等长鞭毛，极少数具有1条鞭毛。色素体中含有叶绿素a、叶绿素c、β-胡萝卜素及叶黄素。色素体常呈黄绿色，1个或多个，盘状、片状。少数为带状或杯状，多数种类为单核。同化产物为油滴、金藻昆布糖及脂肪。约有75属370多种。

繁殖多为无性的，产生动孢子、不动孢子或静孢子，静孢子有时形成孢囊，内生、易于硅化。多数种类喜钙，尤喜生活于半流动的、清洁水体中，蛇胞藻属为淡水普生性的，也生活在污水中。大部分种类可作鱼的饵料。

Yellow-green algae or xanthophytes are an important group of heterokont algae. Most live in freshwater, but some are found in marine and soil habitats. They vary from single-celled flagellates to simple colonial and filamentous forms. Xanthophyte chloroplasts contain the photosynthetic pigments Chlorophyll a, Chlorophyll c, β-Carotene, and the carotenoid diadinoxanthin. Unlike other heterokonts, their chloroplasts do not contain fucoxanthin, which accounts for their lighter colour. Its storage polysaccharide is chrysolaminarin. Xanthophyte cell walls are produced of cellulose and hemicellulose. They appear to be the closest relatives of the brown algae.