Hadar (Beta Centauri) is the eleventh-brightest star in the night sky and a hierarchical triple system about 390 light-years away. The inner pair — components Aa and Ab — are massive B-type stars of 12.0 and 10.6 solar masses orbiting each other every 357 days on a highly eccentric path with separations between 0.5 and 5 AU. A third star, component B, is a B1 dwarf of about 4.5 solar masses on a wide 181-year orbit. Such triple hierarchies are common among massive stars and influence their evolution: close binary interactions can transfer mass, trigger mergers, and produce exotic supernova types. Beta Centauri anchors the southern Cross asterism.