在广义相对论中，绝对视界线（Absolute horizon）是一种时空的界线，完全隔绝因果关系，也就是说在绝对视界线的一端发生的事绝对不会影响绝对视界线的另一端的事，而且任何事物穿越绝对视界线就无法回来。在宇宙中，绝对视界线存在的例子大概就只有黑洞了，对其来说，绝对视界线就是黑洞的边缘也可以说是事件视界，但其实绝对视界线只是事件视界的一种。

In general relativity, an absolute horizon is a boundary in spacetime, defined with respect to the external universe, inside which events cannot affect an external observer. Light emitted inside the horizon can never reach the observer, and anything that passes through the horizon from the observer's side is never seen again. An absolute horizon is the boundary of a black hole by definition.