The ATLAS Collaboration has recently reported the first observation of quantum entanglement in top quark pair production at the Large Hadron Collider (LHC). A brief review of the experimental status of top quark pair spin correlations is given, before highlighting the expected differences between classical and quantum correlations. A criterion for the detection of spin entanglement in top quark pairs has been proposed; the experimental strategy to implement it and observe the effect is discussed, and the positive results of the ATLAS measurement are presented.