Toowoomba Grammar School is an independent, non-denominational, day and boarding grammar school for boys, in East Toowoomba, Toowoomba, Toowoomba Region, Queensland, Australia.

Toowoomba Grammar was established in 1875, the third school to be established under the Grammar Schools Act 1860. It has a non-selective enrolment policy and currently caters for approximately 1,169 students from Prep to Year 12, including 300 boarders from Years 5 to 12.

Some of the Toowoomba Grammar School buildings are listed on the Queensland Heritage Register.

The school was founded in 1875 as a consequence of the Grammar Schools Act of 1860 passed by Queensland's first parliament. The original building was designed by Willoughby Powell. The foundation stone was laid on 5 August 1875; it was to be laid by the Governor of Queensland, William Cairns but due to his illness, Justice Charles Lilley performed the ceremony. A bottle (time capsule) was placed in a cavity in the stone containing two local newspapers, coins of the realm and a parchment commemorating the event and listing the names of the foundation trustees:

the architect and contractor:

and the aldermen of Toowoomba:

The building was completed in 1876. It was officially opened on Thursday 1 February 1877.

The school has been a member of the Great Public Schools' Association Inc (GPS) since 1920. It is also affiliated with the Australian Boarding Schools Association (ABSA), the Association of Heads of Independent Schools of Australia (AHISA), the Junior School Heads Association of Australia (JSHAA), and Independent Schools Queensland (ISQ).