Sh2-308 (Sharpless 308, RCW 11, LBN 1052), commonly known as the Dolphin Head Nebula, is an emission nebula and Wolf-Rayet bubble located in the constellation Canis Major. Its most commonly cited distance is approximately 4,530 light-years (1,389 parsecs), based on Hipparcos satellite astrometric data (2007 validation). Distance estimates in the literature range from approximately 1,875 to 5,870 light-years.

The nebula spans approximately 60 light-years in physical diameter and covers about 35 arcminutes on the sky. It is an HII region composed of ionised hydrogen, shaped by the stellar winds of the central Wolf-Rayet star EZ Canis Majoris (WR 6, HD 50896, EZ CMa), spectral type WN4b, apparent magnitude 6.71–6.95. Sh2-308 is one of only two known Wolf-Rayet bubbles that emit X-rays, alongside NGC 6888 (Crescent Nebula).

EZ Canis Majoris has expelled its outer hydrogen layers and its powerful stellar winds continue to drive the surrounding ionised gas outward. The nebula is estimated to have formed approximately 70,000 years ago. Sh2-308 was among the first three ring nebulae identified around Wolf-Rayet stars.

Catalogued by American astronomer Stewart Sharpless in his revised catalogue of HII regions, published in 1959.

Also visible in the field: Sh2-303, an HII region to the left of the main bubble, ionised by the same Wolf-Rayet star WR 6; MPA J0656-2356, a likely planetary nebula (round morphology, ~170 arcsec apparent diameter) on the lower perimeter of Sh2-308, with a DAO-type white dwarf central star (~80,000 K); and PK 233-10.1, a catalogued planetary nebula above the Sh2-303 cloud, extremely compact and stellar in appearance at low magnification.

Imaged as a 2-panel mosaic from Starfront Observatories, Rockwood, Texas, USA.