Analgesics are medicines that are used to relieve pain (provide analgesia). They are also known as painkillers. Technically, the term analgesic refers to a medication that relieves pain without loss of consciousness, as opposed to an anesthetic, which is a substance that induces insensitivity to pain via a loss of consciousness and an absence of sensory perception.

A large number of medicines have pain-relieving properties, and analgesics with similar mechanisms of action are usually grouped together; for example, nonsteroidal anti-inflammatory drugs (NSAIDs) and opioids (narcotics). Analgesics can also be grouped depending on the severity of pain they are indicated for, for example, acetaminophen and NSAIDs are indicated for mild-to-moderate pain, and weak opioids, such as , or tramadol are indicated for moderate-to-severe pain.

Central nervous system analgesics act in the brain or spinal cord to produce their effects; examples include opioids such as morphine and oxycodone. Peripherally acting analgesics act outside of the brain and spinal cord and include NSAIDs and COX-2 inhibitors.