Annulus (or anulus) or annular indicates a ring- or donut-shaped area or structure. It may refer to:

• Anulus fibrosus disci intervertebralis, spinal structure
• Annulus of Zinn, a.k.a. annular tendon or anulus tendineus communis, around the optic nerve
• Annular ligament (disambiguation)
• Digitus anularis, a.k.a. ring finger
• Anulus ciliaris, a.k.a. ciliary body
• Anulus femoralis, a.k.a. femoral ring
• Anulus inguinalis superficialis, a.k.a. superficial inguinal ring
• Anulus inguinalis profundus, a.k.a. deep inguinal ring
• Anuli fibrosi cordis, a.k.a. fibrous rings of heart
• Anulus umbilicalis , a.k.a. umbilical ring

• Annulus (botany), structure on fern and moss sporangia
• Annulus (mycology), structure on mushroom
• Annulus (zoology), an external circular ring

• Annulus (construction), outer gear ring in an epicyclic gearing
• Annular lake, a ring-shaped lake caused by meteor impact
• Annulus (mathematics), the shape between two concentric circles
• Annulus (firestop), site of construction issue
• Annular piston, a ring-shaped piston
• Annulus (well), void between concentric cylinders
• Annular blowout preventer, device for sealing oil and gas wells
• Annulation, type of ring-producing chemical reaction

• All pages with titles beginning with annulus
• All pages with titles containing annulus
• Annulet (disambiguation)
• Annular eclipse
• Annular tropical cyclone
• Annular combustor, design option in engine
• Ring (disambiguation)