挖掘机，又称挖土机（香港俗称鸡头、掘泥车，在**常称为怪手），是一种特殊的工程车辆，是由旋转平台、大型铲子以及机械手臂组成。一般是以履带或车轮行进。由于它的样子特殊，行内对其有各种称呼，如怪手、反铲、挖机等。 旋转平台可以做360度回转的挖土机，从最小型的小松PC01、日立EX4、石川岛IS4J、神户制钢SK005到最大型的小松PC8000、利勃海尔98 00、日立EX8000。在挖掘机的转盘中心部份，都有1个回转分流盘（joint Ass'y）设备，外壳固定在上部机械上面有6~9条油管，中心轴固定在下部机械也有6~9条油管，可做360度旋转，它的用途是将上部机械的液压油，分送到底盘结构中的行走油压马达组，带动履带然后走动，或是操作推土板，所以挖掘机上半部要360度旋转几次都可以。

Excavators (Hydraulic Excavators) are heavy construction equipment consisting of a boom, dipper (or stick), bucket and cab on a rotating platform known as the "house". The house sits atop an undercarriage with tracks or wheels. They are a natural progression from the steam shovels and often mistakenly called power shovels. All movement and functions of a hydraulic excavator are accomplished through the use of hydraulic fluid, with hydraulic cylinders and hydraulic motors. Due to the linear actuation of hydraulic cylinders, their mode of operation is fundamentally different from cable-operated excavators which uses winches and steel ropes to accomplish the movements.