The ten largest stars ever measured, ranked by solar radii — led by the red hypergiant Stephenson 2-18, whose diameter would swallow Saturn's orbit.
Quick answer: 1. Stephenson 2-18 (Stephenson 2 DFK 1), 2. Westerlund 1-26, 3. VY Canis Majoris, 4. Mu Cephei (Herschel's Garnet Star), 5. RW Cephei, 6. WOH G64, 7. V354 Cephei, 8. SMC 018136 (SP77 46-44), 9. KY Cygni, 10. V766 Centauri (HR 5171A).
These are the largest stars known to astronomy, ranked by radius relative to the Sun. Most are red hypergiants or cool supergiants in the late stages of stellar evolution — bloated, dying giants that have expanded to hundreds or thousands of times the Sun's diameter. The size champion is Stephenson 2-18 (also known as Stephenson 2 DFK 1), a red supergiant in the Scutum constellation whose radius of roughly 2,150 solar radii means that if placed at the centre of our solar system, its surface would extend beyond the orbit of Saturn. Close behind are the red hypergiants Westerlund 1-26 and VY Canis Majoris, each so vast that light takes hours to cross them. All radii in this list carry significant uncertainty — these stars are distant (most in the Milky Way's galactic plane, tens of thousands of light-years away), have no solid surface, and their angular diameters push the limits of interferometric measurement. The figures below represent the best consensus estimates as of 2025–2026 from peer-reviewed stellar catalogues.
The largest known star, a red supergiant or hypergiant in the Scutum constellation with an estimated radius of about 2,150 solar radii — large enough to envelop Saturn's orbit if placed at the Sun's position.
A red supergiant or hypergiant in the massive cluster Westerlund 1, with a radius estimated at 1,530–2,550 solar radii, making it one of the largest stars ever identified.
A famous red hypergiant in Canis Major, historically considered the largest known star; recent GAIA-calibrated estimates place its radius at roughly 1,420 solar radii.
A bright red supergiant and one of the largest stars visible to the naked eye, Mu Cephei shines with a deep garnet hue and spans roughly 1,260 solar radii.
A yellow-white hypergiant that fluctuates in brightness and size; its mean radius is estimated at about 1,200 solar radii, placing it among the Galaxy's most voluminous stars.
A red supergiant in the Large Magellanic Cloud, WOH G64 is surrounded by a thick torus of ejected material; its radius is estimated at about 1,080 solar radii, making it the largest known extragalactic star.
A red supergiant in the Cepheus OB1 association, with an estimated radius of roughly 1,060 solar radii and an irregular variability pattern typical of the most evolved supergiants.
A red supergiant in the Small Magellanic Cloud, this star's radius is estimated at roughly 1,020 solar radii, making it one of the most extended stars known outside the Milky Way.
A red supergiant in the Cygnus constellation with an estimated radius of about 950 solar radii, its variability has been observed for more than a century.
A yellow hypergiant that was once thought to be the largest star ever measured; revised GAIA distances place its radius at roughly 900 solar radii, still comfortably among the top ten.
| # | Name | type | constellation | distance | luminosity |
|---|---|---|---|---|---|
| 1 | Stephenson 2-18 (Stephenson 2 DFK 1) | Red supergiant / hypergiant | Scutum | ~20,000 ly | ~440,000 L☉ |
| 2 | Westerlund 1-26 | Red supergiant / hypergiant | Ara | ~13,000 ly | ~380,000 L☉ |
| 3 | VY Canis Majoris | Red hypergiant | Canis Major | ~3,800 ly | ~270,000 L☉ |
| 4 | Mu Cephei (Herschel's Garnet Star) | Red supergiant | Cepheus | ~2,800 ly | ~280,000 L☉ |
| 5 | RW Cephei | Yellow hypergiant | Cepheus | ~8,000 ly | ~500,000 L☉ |
| 6 | WOH G64 | Red supergiant | Dorado | ~160,000 ly (LMC) | ~280,000 L☉ |
| 7 | V354 Cephei | Red supergiant | Cepheus | ~8,800 ly | ~220,000 L☉ |
| 8 | SMC 018136 (SP77 46-44) | Red supergiant | Tucana | ~200,000 ly (SMC) | unknown |
| 9 | KY Cygni | Red supergiant | Cygnus | ~5,000 ly | ~200,000 L☉ |
| 10 | V766 Centauri (HR 5171A) | Yellow hypergiant | Centaurus | ~11,700 ly | ~300,000 L☉ |
Stars are ranked by estimated radius in solar units (R☉), where 1 R☉ = 695,700 km (the Sun's radius). Radii are drawn from the NASA ADS peer-reviewed literature, the revised GAIA DR3/DR4 distance calibrations, and the JPL Stellar Parameters Catalogue. Only stars with published angular-diameter or SED-fit measurements in refereed journals are included; theoretical model-only estimates are excluded. Many of these stars are variable (semi-regular, slow irregular), so the listed radius is the published mean or most-cited value. Rank 1 is the largest. Where a star has multiple published measurements, the most recent GAIA-calibrated figure is preferred.
Stephenson 2-18 (Stephenson 2 DFK 1) is the largest known star, with a radius of roughly 2,150 times that of the Sun. If it replaced the Sun in our solar system, its surface would extend past the orbit of Saturn.
Astronomers measure stellar radii primarily through angular-diameter interferometry (directly resolving the star's disc with telescopes like VLTI), plus SED (spectral energy distribution) fitting combined with GAIA parallax distances. Indirect methods include eclipsing binary analysis and luminosity-temperature relations.
VY Canis Majoris was long considered the largest star, but improved GAIA distance measurements and interferometric observations in the 2010s–2020s revised its radius downward from earlier estimates above 2,000 R☉ to about 1,420 R☉, while deeper surveys found larger stars in distant clusters.
Yes — all stars on this list exceed 700 solar radii, which means even the smallest (#10, V766 Centauri) would swallow Earth's orbit (215 R☉) several times over. Stephenson 2-18 at 2,150 R☉ would reach past Saturn's orbit (about 1,950 R☉).