The temperature of Regulus, the brightest star in the constellation Leo, is estimated to be around 12,600 Kelvin (12,327 degrees Celsius or 22,221 degrees Fahrenheit).

This makes Regulus a very hot star, significantly hotter than our Sun, which has a surface temperature of around 5,500 Kelvin.

Keep in mind that this is just an estimate, and the actual temperature can vary slightly depending on the method used for measurement.