134 Sophrosyne is a large main-belt asteroid that was discovered by German astronomer Robert Luther on 27 September 1873, and was named after the concept of sophrosyne, Plato's term for 'moderation'.

Classified as a C-type asteroid, it has an exceedingly dark surface and most probably a primitive carbonaceous composition.

[citation needed] An occultation of a star by 134 Sophrosyne was observed 24 November 1980, in the United States.

Timing information from this event allowed a diameter estimate of 110 km to be derived.

[6] Photometric observations of the asteroid in 2015 produced a lightcurve indicating a rotation period of 17.190±0.001 h with a variation amplitude of 0.28±0.01 in magnitude.