• Animal shell, or exoskeleton, including those of molluscs, turtles, insects and crustaceans
• Seashell, the shells of various marine animals, especially marine mollusks
• Eggshell, the outer covering of a hard-shelled egg

Any more or less hollow surface covering, including:

• Shell (projectile), a projectile which carries an explosive payload
• Shell (theater), a curved surface for reflecting and focusing sound
• Racing shell, a rowed watercraft
• Thin-shell structure, a method of building construction

In science and mathematics:

• Shell (mathematics), a ring-like algebraic structure
• Electron shell, describing the structure of electron configuration in atoms
• Electron shells in atomic physics
• On shell and off shell, in quantum field theory

In computing

• Shell (computing), a type of computer user interface (for example a Unix or a DOS shell)
• Shell account, a personal account that gives a user access to a Unix shell on another machine, usually through SSH
• Shell sort, a sorting algorithm

In business

• Royal Dutch Shell, a multinational energy company
• Shell Oil Company, American affiliate
• Shell Canada
• Shell Nigeria
• Showa Shell Sekiyu K.K., in Japan.
• Shell Turbo Chargers, a defunct basketball team in the Philippines under the ownership of the Shell Corporation.
• Shell, Ecuador, sometimes called Shell Mera, a city named after the Shell Oil Company
• Shell (corporation)

In media and entertainment:

• Shell Thropp, a character from the books Wicked and Son of a Witch
• "Shells" (Angel), a 2004 episode of the television series Angel
• The Shells, an American doo wop group
• Big Shell, an offshore decontamination facility in the videogame Metal Gear Solid 2: Sons of Liberty

As a surname:

• Donald Shell, American computer scientist
• Art Shell, former American football player and coach