Simha is the fifth rashi, the Vedic sign of the lion, corresponding to Leo. In jyotisha it is the only sign ruled by the Sun (Surya). Its quality is fixed (sthira), and its element is fire (agni tattva). Jyotisha reads Simha through the Sun's sovereignty and the lion's pride: authority, dignity, self-expression, and the will to lead and be seen. As a sidereal sign it is anchored to the fixed stars and sits roughly 24 degrees behind tropical Leo, so the royal star Regulus, at the lion's heart, falls near the start of sidereal Simha. The Sun's sole rulership of the lion is shared with Western astrology. Jyotisha places particular weight on the Sun here as the significator of the soul, the father, and status.
Simha, lion, is a direct translation of the Greek leon, arriving in Sanskrit through the Yavanajataka, a versification of a Greek astrological text of roughly the second through fourth centuries CE, itself built on the older twelve-sign scheme Babylonian celestial divination had fixed by roughly the fifth or fourth century BCE; no twelve-sign zodiac of any kind is attested anywhere in the earlier Vedic corpus. The Sun's sole rulership of Simha, one of only two signs any planet governs alone alongside the Moon's rulership of Karka, belongs to a later classical layer of the tradition, standardly credited to compilations such as the Brihat Parashara Hora Shastra of roughly the seventh or eighth century CE, whose ascription to the sage Parashara is itself a later, pseudepigraphic attribution rather than the work of a single historical author.
Sources Brihat Parashara Hora ShastraSage Parashara (attributed) with The Yavanajataka of SphujidhvajaDavid Pingree, Jyotihsastra: Astral and Mathematical LiteratureDavid Pingree