A calibrator star is a star that is typically used for calibration purposes on high-sensitized sensors located on space telescopes.

Calibrator stars do not usually follow a specific criteria, but are normally hand-picked for different reasons.

Infrared and optically bright stars may be observed for calibration purposes by satellites, particularly those with sensitivity to both infrared and visible radiation. The stars chosen generally meet the following criteria: they have a visual magnitude that is equal to or less than +6, and an IR brightness (in the 1-5 micrometer range) greater than that of Vega.

The stars are strictly southern objects (i.e., their declinations are negative), and most are cool stars of spectral classes K and M. While these are not the only stars that might serve for these purposes, they are well distributed across the southern sky and some should be visible at all times.

A catalog of recommended calibrator stars does exist, with 1,510 stars being listed. The catalog gives the magnitude, mass and other statistics.