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LIGO’s successful detection of gravitational waves has revitalized the theoretical understanding of the angular momentum carried away by gravitational radiation. An infinite-dimensional “supertranslation ambiguity” has presented an essential difficulty for studying angular momentum at null infinity. In this talk, we will present a definition of angular momentum in general relativity that is supertranslation invariant. The new definition of angular momentum is derived from the limit of the Chen-Wang-Yau quasilocal angular momentum. The talk is based on joint work with Po-Ning Chen, Jordan Keller, Mu-Tao Wang and Shing-Tung Yau.