朱利亚集合（又译为茹利亚集合，英文：Julia set）是一个在复平面上形成分形的点的集合。以法国数学家加斯顿·朱利亚（Gaston Julia）的名字命名。

朱利亚集合可以由下式进行反复迭代得到：

对于固定的复数c，取某一z值（如），可以得到串行

这一串行可能发散于无穷大或始终处于某一范围之内并收敛于某一值。我们将使其不扩散的z值的集合称为朱利亚集合。

In the context of complex dynamics, a topic of mathematics, the Julia set and the Fatou set are two complementary sets (Julia 'laces' and Fatou 'dusts') defined from a function. Informally, the Fatou set of the function consists of values with the property that all nearby values behave similarly under repeated iteration of the function, and the Julia set consists of values such that an arbitrarily small perturbation can cause drastic changes in the sequence of iterated function values. Thus the behavior of the function on the Fatou set is 'regular', while on the Julia set its behavior is 'chaotic'.