在电子学中，信号边缘（英语：signal edge），或称信号边沿，是数字信号在两种逻辑电平（0或1）之间转变的状态。由于数字信号电平由方波来表示，因此这种状态的变化被称为“边缘”。

信号的一个上升沿（rising edge）是数字信号从低电平向高电平的转变。当一个电路为上升沿触发的（rising edge-triggered），当接入的定时器信号由低电平向高电平转变，触发器电路被触发，而当它从高电平向低电平的转变则被忽略。

与上升沿对应的概念为下降沿（falling edge），它是指数字信号从高电平向低电平的转变，当一个电路为下降沿触发的（falling edge-triggered），当接入的定时器信号由高电平向低电平转变，触发器电路被触发，而当它从低电平向高电平的转变则被忽略。

In electronics, a signal edge is a transition in a digital signal either from low to high (0 to 1) or from high to low (1 to 0). It is called an "edge" because the square wave which represents a signal has edges at those points.

A rising edge is the transition from low to high. It is also named positive edge. When a circuit is rising edge-triggered, it becomes active when its clock signal goes from low to high, and ignores the high-to-low transition.