鱼眼镜头指视角接近或等于180°的镜头，视角为众多镜头之冠。这类镜头一般焦距极短，在135底片格式下，16毫米或焦距更短的镜头通常即可认为是鱼眼镜头，绝大部分的鱼眼镜头均是定焦镜头，只有少部分是变焦镜头。依成像可分为圆形鱼眼（Circular fisheye，又称全周鱼眼，画面呈圆形）与对角线鱼眼（Diagonal fisheye或Full-frame fisheye，画面呈方形）其镜面似鱼眼向外凸出，所视的景物，像鱼由水中看水面的效果。鱼眼镜头一般用来拍摄广阔的风景或于室内拍摄。不少摄影师喜欢使用鱼眼镜的夸张变形来营造透视感。历史上最广的鱼眼镜头是艺康旗下的6毫米f/2.8，视角接近220°。而富士能研发了世界首台用于五百万像素CCD摄像机的185°广角全方位镜头。

A fisheye lens is an ultra wide-angle lens that produces strong visual distortion intended to create a wide panoramic or hemispherical image. Fisheye lenses achieve extremely wide angles of view by forgoing producing images with straight lines of perspective (rectilinear images), opting instead for a special mapping (for example: equisolid angle), which gives images a characteristic convex non-rectilinear appearance.