• Companion (caregiving), a nurse assistant or similar professional who assists a patient one-on-one
• Companion (ship), an architectural feature of ships
• Companion animal, a pet animal kept for companionship
• Companion parrot, a pet parrot that interacts with its owner
• Companion star, a star in a binary star system
• Companion weapon, an object held in the non-sword hand while fencing
• Muhammad's companions, the Sahaba
• Companion cavalry, Alexander the Great's elite cavalry
• Foot Companion, the primary type of soldier in Alexander the Great's army
• Lady's companion, a genteel woman who acted as a companion for woman of rank or wealth
• Companion planting, planting of different crops in close physical proximity
• A handbook or guide book or compendium e.g. Star Trek: Deep Space Nine Companion or The Oxford Companion to Music
• A member of a Holy Royal Arch chapter
• A domestic partner
• A concubine

Fiction

• Companion (Doctor Who), a character who travels with the Doctor in the TV series Doctor Who
• Companion (Firefly), a type of courtesan and entertainer in the TV series Firefly
• The Companions or Heroes of the Lance, a group of heroes in the fictional Dragonlance world
• Companion (manga), an ongoing manga series published in Kodansha's Magazine Z

Music

• Companion (Patricia Barber album), a (1999) album by Patricia Barber