| component1 = 54 Leo A
| names1 = HD 94601, HR 4259, SAO 81583
| component2 = 54 Leo B
| names2 = HD 94602, HR 4260, SAO 81584
}}{{Starbox reference
| Simbad=54+Leo
}}{{Starbox end}}54 Leonis is a binary star[29] system in the zodiac constellation of Leo, located around 321[4] light years from the Sun. It is visible to the naked eye as a faint, white-hued star with a combined apparent visual magnitude of 4.30.[31] As of 2017, the pair had an angular separation of {{val|6.60|ul=arcsecond}} along a position angle of 113°.[32] They have a physical separation of around {{Convert|533|AU|Gm|lk=on|abbr=on}}.[21]The magnitude 4.477[3] primary, designated component A, is an A-type main-sequence star with a stellar classification of A0 V,[7] which indicates it is generating energy through hydrogen fusion at its core. It has a high rate of spin, showing a projected rotational velocity of 185 km/s. This is giving the star an oblate shape with an equatorial bulge that is an estimated 8% larger than the polar radius.[24] The star
is roughly 411[20] million years old with 2.4[20] times the mass of the Sun and about 2.88[21] times the Sun's radius.
The fainter magnitude 6.29[6] secondary, component B, is a smaller A-type main-sequence star with a class of A2 Vn.[7] The 'n' suffix indicates wide "nebulous" lines due to rapid rotation. It is spinning with an even higher projected rotational velocity of 250[21] km/s. The star has about 2.59[21] times the Sun's radius.
Asteroid 729 Watsonia occulted HIP 53417 on March 3, 2013 at 01:48.[44]
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