Probable binary star system in the constellation Lupus
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! style="text-align: center; background-color: #FFFFC0;" colspan="2" | Observation dataEpoch J2000.0
       Equinox J2000.0 (ICRS)
! style="text-align:left" | Constellation
! style="text-align:left" | Right ascension
! style="text-align:left" | Declination
! style="text-align:left" | Apparent magnitude (V)
! style="background-color: #FFFFC0; text-align: center;" colspan="2"| Characteristics
! style="text-align:left" | Spectral type
! style="text-align:left" | U−B 
! style="text-align:left" | B−V 
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Xi1 Lupi (ξ1 Lup, ξ1 Lupi) is a probable binary star in the southern constellation of Lupus. It is faintly visible to the naked eye with an apparent visual magnitude of 5.1, and forms a visual double star with Xi2 Lupi. Based upon an annual parallax shift of 23.60 mas as seen from Earth, it is located around 140 light-years from the Sun. It is a member of the Upper Scorpius sub-group of the nearby Sco OB2 association.
This star shows periodic radial velocity variations that can be best explained as a spectroscopic binary system. The visible component is an A-type main-sequence star with a stellar classification of A3 V. It has twice the mass of the Sun and shines with about 12 times the Sun's luminosity from its outer atmosphere at an effective temperature of . The star is an estimated 237 million years old and is spinning with a projected rotational velocity of 78 km/s.
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