九点圆（又称欧拉圆、费尔巴哈圆），在平面几何中，对任何三角形，九点圆通过三角形三边的中点、三高的垂足、和顶点到垂心的三条线段的中点。九点圆定理指出对任何三角形，这九点必定共圆。而九点圆还具有以下性质：

In geometry, the nine-point circle is a circle that can be constructed for any given triangle. It is so named because it passes through nine significant concyclic points defined from the triangle. These nine points are:

The nine-point circle is also known as Feuerbach's circle, Euler's circle, Terquem's circle, the six-points circle, the twelve-points circle, the n-point circle, the medioscribed circle, the mid circle or the circum-midcircle. Its center is the nine-point center of the triangle.