Tsvi Piran (Hebrew: צבי פיראן; born May 6, 1949) is an Israeli theoretical physicist and astrophysicist, best known for his work on Gamma-ray Bursts (GRBs) and on numerical relativity.

In 1985 he wrote the first numerical code calculating the collapse and formation of a rotating black hole[11] and the resulting gravitational radiation waveform.

Detection of this waveform in the future by advanced gravitational radiation detectors might provide the ultimate proof of the existence of a black hole.

He went on later to show that, in fact, the onset of inflation is not fully generic and it requires specific initial conditions,[13] a concept whose full implications have not been addressed up to now.

[14] Piran's work includes also contributions to the general theory of relativity such as one of the strongest counter examples to the cosmic censorship hypothesis[15] and the demonstration of the instability of the inner structure of a black hole.