The Devonian is the fourth period of the Paleozoic era and the Phanerozoic eon. It lasted from about 419 million years ago (mya) to about 359 mya. It is named after Devonshire, England, where rocks from this period were first studied.

Sea levels were high, and there was a great variety of fish and other marine organisms. The Devonian fish included the Agnatha (jawless fish), the Acanthodii (spiny fish), the Placoderms (armoured fish), the Chondrichthyes (cartilaginous fish), and the early Osteichthyes (bony fish). The Devonian strata are divided into lower, middle and upper subdivisions.

Tiktaalik was an extinct tetrapodomorph that lived during the Devonian.