羽纹硅藻目（学名：Pennales），是硅藻纲两个目的其中一个，另一为中心硅藻目。与中心硅藻目不同，在形体上如以切顶线进行观察，此目生物大致呈左右对称，而圆心硅藻目则多呈辐射对称。
壳面花纹羽纹状排列，左右对称或不对称，有壳缝、假壳缝、管壳缝；形状多种，单细胞或群体；色素体盘状、板状、星状；花纹为孔纹、线纹、肋纹、龙骨；壳面线形、椭圆形、卵形、S形、舟形、新月形等；带面长形、梯形。

Order Pennales is a traditional subdivision of the heterokont algae known as diatoms. The order is named for the shape of the cell walls (or valves or frustules) of pennate diatoms, which are elongated in valve view. The valves may be linear or oval in shape, and usually bear bilaterally symmetrical ornamental patterns. These patterns are composed of a series of transverse lines (known as striae) that can appear as rows of dots when viewed with an optical microscope. Some pennate diatoms also exhibit a fissure along their longitudinal axis. This is known as a raphe, and is involved in gliding movements made by diatom cells; motile diatoms always possess a raphe.