立体交汇（英语：flying junction, grade-separated juntion or flyover）是指在铁路或道路的多线并行区间，且通常是分流或汇合处，采用跨线桥的形式使部分股道跨越其他股道，从而避免车辆运行线路冲突。通常也称为立体交叉、立体疏解、公／铁路立体化。立交的另一种形式是下穿式立交（burrowing junction或diveunder），即侧线或支线从正线或干线下方穿越。

与以上两种立交形式相对应的是平面交汇（level juntion或flat junction），即不同方向的股道在同一水平面交叉，此交叉形式会产生敌对进路（conflicting routes），需要通过联锁信号保证行车安全。

A flying junction or flyover is a railway junction at which one or more diverging or converging tracks in a multiple-track route cross other tracks on the route by bridge to avoid conflict with other train movements. A more technical term is "grade-separated junction". A burrowing junction or dive-under occurs where the diverging line passes below the main line.