Several methods, including:

• From chlorobenzene- Dow's process: Chlorobenzene is treated with NaOH at high temperature and pressure, followed by acidification to yield phenol.
• From cumene- Cumene (isopropylbenzene) is oxidized to cumene hydroperoxide, which is then treated with dilute acid to give phenol and acetone. This is an industrially important method.
• From diazonium salts- A diazonium salt is warmed with water or treated with dilute acid to yield phenol, nitrogen gas, and an acid (e.g., HCl).