Flamsteed designations for stars were developed by astronomer John Flamsteed for his early-1700s astronomical catalog Catalogus Britannicus, which covered stars visible from England. It groups stars by constellation indicating its individual stars by a Latin form of the constellation (optionally abbreviated) with a preceding number. Examples: 51 Pegasi, 61 Cygni.
Some stars are still sometimes referred to by this type of designation (but far fewer than those referred to by the more common Bayer designations that indicates the individual stars by Greek letters), and extra-solar planets associated with them are often indicated by using the designation with a subsequent letter, starting with "b" for the first planet discovered, e.g., 55 Cancri e orbiting the star 55 Cancri in the constellation Cancer.
Hevelius designations and Bode designations are two other early systems that similarly numbered the stars within constellations (but differing in which star had which number) but very few of their designations are still in common use. The more recent Gould designation is also similar, and is now commonly indicated with a "G" after the number, for example, 41 G. Arae.