赫氏空隙（Hertzsprung gap）是赫罗图上恒星团的一种特色。它是依据埃希纳·赫茨普龙的发现命名的，他首先注意到在赫罗图上光谱类型A5到G0和绝对星等+1到-3的这一块区域(也就是在主序带上方到大约是1.5太阳质量的红巨星)是缺乏恒星的。当一颗恒星在演化过程中跨越了赫氏空隙，就意味着它已经结束氢核燃烧，但尚未开始氦核燃烧。

恒星不会停留在赫氏空隙上，这是因为它们在赫罗图上的经过这一区域的迁徙非常快速(只有数千年，相较于恒星的生命周期是非常短暂的) )，在图中这一部分的恒星密度非常的低，在依巴谷卫星11,000颗恒星的完整赫罗图上显示，还是有一小撮恒星在这个区域。

The Hertzsprung gap is a feature of the Hertzsprung–Russell diagram for a star cluster. It is named after Ejnar Hertzsprung who first noticed the absence of stars in the region of the Hertzsprung–Russell diagram between A5 and G0 spectral type and between +1 and −3 absolute magnitudes (i.e. between the top of the main sequence and the red giants for stars above roughly 1.5 solar mass (M_☉)). When a star during its evolution crosses the Hertzsprung gap, it means that it has finished core hydrogen burning, but is yet to start hydrogen shell burning.