Aristyllus (fl. ca. 261 BC) was a Greek astronomer, presumably of the school of Timocharis (c.300 BC). He was among the earliest meridian-astronomy observers.Six of his stellar declinations are preserved at Almajest 7.3. All are exactly correct within his over-cautious rounding to 1/4 degree. See discussion (and lessons) at DIO 7.1 ‡1 p. 13 (2007). A lunar crater, Aristillus, aptly near the Moon's meridian and at a lunar latitude roughly equal to the terrestrial latitude of Alexandria, is named after him.