In Buddhism, a mental fetter, chain or bond (Pāli: samyojana, Sanskrit: संयोजना, romanized: saṃyojana) shackles a sentient being to saṃsāra, the cycle of lives with dukkha. By cutting through all fetters, one attains nibbāna (Pali; Skt.: निर्वाण, nirvāṇa).

Throughout the Pali canon, the word "fetter" is used to describe an intrapsychic phenomenon that ties one to suffering. For example, in the Itivuttaka, the Buddha says:

"Monks, I don't envision even one other fetter — fettered by which beings conjoined go wandering and transmigrating on for a long, long time—like the fetter of craving (taṇhā). Fettered with the fetter of craving, beings conjoined go wandering & transmigrating on for a long, long time.

— Buddha, in Khuddaka Nikaya, Itivuttaka 1.15

Elsewhere, the suffering caused by a fetter is implied as in this more technical discourse from Samyutta Nikaya 35.232, where Ven. Sariputta converses with Ven. Kotthita:

Ven. Kotthita: "How is it, friend Sariputta, is ... the ear the fetter of sounds or are sounds the fetter of the ear?..."
Ven. Sariputta: "Friend Kotthita, the ... ear is not the fetter of sounds nor are sounds the fetter of the ear, but rather the desire and lust that arise there in dependence on both: that is the fetter there...."

— Samyutta Nikaya

The fetters are enumerated in different ways in the Pali canon's Sutta Pitaka and Abhidhamma Pitaka.