额肌是一块薄薄的人体肌肉，位于前额，呈四边形，and intimately adherent to the superficial fascia。额肌比枕肌更宽，其纤维长度更长、颜色更白。

它并不附着任何骨质。

额肌中央的部分纤维和降眉间肌相连，其边缘纤维更和皱眉肌和眼轮匝肌边缘相混合，再会合眉毛之处的皮肤，其侧面纤维are also blended with the latter muscle over the zygomatic process of the 额骨。

额肌的主要功能就在于提起眉毛（thus opposing the orbital portion of the orbicularis），尤其当眼睛朝上看或眼前事物太远、太暗时起作用，人在感觉诧异的时候也会收缩额肌。另一个看似无用的作用是把头皮向前拉，相反于枕肌收缩的动作。

The frontalis muscle (frontal belly) is muscle which covers parts of the skull. Some sources consider the frontalis muscle to be a distinct muscle. However, Terminologia Anatomica currently classifies it as part of the occipitofrontalis muscle along with the occipitalis muscle.