宏区块（Macroblock）是一种影像压缩的术语。

宏区块是运动预测的基本单位，一张完整的图像（frame）通常会被切割成几个宏区块，MPEG2和较早期的codec定义宏区块都是8x8 pixels.现代的一点codec像是h.263和h.264的宏区块通常都是16x16 pixels和相应区域内的Cb、Cr色差信号阵列共同组成。

宏区块为基准来选择特定的预测类型，而非整个图像都使用同样的类型：

Macroblock is a processing unit in image and video compression formats based on linear block transforms, such as the discrete cosine transform (DCT). A macroblock typically consists of 16×16 samples, and is further subdivided into transform blocks, and may be further subdivided into prediction blocks. Formats which are based on macroblocks include JPEG, where they are called MCU blocks, H.261, MPEG-1 Part 2, H.262/MPEG-2 Part 2, H.263, MPEG-4 Part 2, and H.264/MPEG-4 AVC. In H.265/HEVC, the macroblock as a basic processing unit has been replaced by the coding tree unit.