全画幅数码单镜头反光相机是一类装配有接近传统 35 毫米胶片全尺寸（36 x 24 毫米）的影像传感器的数码单镜反光相机（DSLR）。所强调的全画幅（Full-Frame）是一种基于对比那些具备较小尺寸传感器的机型—— 一般为APS-C规格 ——的分类方式。

在2007年的时候，绝大多数的数码单反相机使用的都是小于 35 毫米规格的传感器——由于较小的尺寸的传感器较为的便宜，且易于处理。

在2008年的下半年，数码单反的几家制造商，佳能，尼康与索尼纷纷推出了自己的中高档135格式全画幅尺寸数码单反相机。此举宣告135全画幅在数码单反市场普及在即。

The term Full Frame is used by D-SLR users as a short-hand for an image sensor format which is the same size as 35mm format (36 mm × 24 mm) film. Historically, 35mm was considered a small film format compared with medium format, large format and even larger. This is in contrast to cameras with smaller sensors (for instance, those with a size equivalent to APS-C-size film), much smaller than a full 35mm frame. Currently, the majority of digital cameras, both compact and SLR models, use a smaller-than-35 mm frame, as it is easier and cheaper to manufacture imaging sensors at a smaller size. Historically, the earliest digital SLR models, such as the Nikon NASA F4 or Kodak DCS 100, also used a smaller sensor. Kodak states that 35mm film has the equivalent of 6,000 pixel horizontal resolution according to a Senior Vice President of IMAX.