扩张性心肌病（英文：Dilated cardiomyopathy or DCM），也称充血性心肌病，表现为心脏功能减弱，各心腔扩大，不能充分泵血。心脏功能的减弱也会影响肺、肝和其它器官。

DCM是心肌病（cardiomyopathies）的一种，主要是心肌（myocardium）功能受到影响。不同的心肌病都有各自影响心脏正常功能的原因。在DCM中，一部分心肌细胞膨大，而且没有明显原因。左心室和（或）右心室的收缩泵功能受损，导致了进一步的心脏肥大。DCM作为一种常见的心肌病，男性发病频率高于女性，发病年龄主要集中于20到60岁。三分之一的充血性心力衰竭（CHF）患者是由于患有DCM。DCM在儿童中也有发现。

Dilated cardiomyopathy or DCM is a condition in which the heart becomes enlarged and cannot pump blood efficiently. The decreased heart function can affect the lungs, liver, and other body systems.

DCM is one of the cardiomyopathies, a group of diseases that affect primarily the myocardium (the muscle of the heart). Different cardiomyopathies have different causes and affect the heart in different ways. In DCM a portion of the myocardium is dilated, often without any obvious cause. Left or right ventricular systolic pump function of the heart is impaired, leading to progressive cardiac enlargement and hypertrophy, a process called remodeling.