Spalding Grammar School (SGS), fully known as The Queen Elizabeth Royal Free Grammar School Spalding, is an 11–18 boys' grammar school in Spalding, Lincolnshire, England. By November 2015, a total of 985 boys were enrolled at the school, 277 of which were enrolled on 16 to 19 study programmes.

The school was founded in 1588 by royal charter, applied for by a Rev. Johnson, and within part of Spalding Parish Church, called St Thomas's Chapel, until the 19th century. It was founded on its current site in 1881.

The school amalgamated with Moulton Grammar School of Moulton in 1939. Moulton Grammar School was founded under the will of John Harrox (died 1561) who was steward to Sir John Harrington of Weston. The School opened in 1562 with ten pupils and continued to educate boys from the district until it amalgamated with Spalding. The old school buildings still exist but are now private residences. The school magazine, The Bentleian, dates to July 1922.

In October 2018, a decision was made by the school to stop sixth form pupils from using "ever-larger bags" to carry books, which were seen by the school as an injury danger to younger pupils. A temporary online petition was organised against the order.

Spalding Grammar School admits pupils aged 11 to 18 from the council district of South Holland - an area of 500 square miles (1,300 km) - some pupils travelling over 20 miles (32 km) to reach the school.

In years 7 to 11, only boys are admitted. In sixth form (years 12 and 13), both boys and girls are admitted. Spalding Grammar is a selective school, and its entrants in the lower school are permitted only by taking the county-wide 11+ tests. The current number of pupils is 985. The sixth form has 277 pupils. There are 68 teaching staff.

The school is in the south of Lincolnshire, on Priory Road in Spalding.

A sports hall was opened by boxer Henry Cooper in November 1993. In January 2006 new buildings were opened for ICT, sociology, technology, English and drama (with a performing arts studio). The Modern Languages lab was also built at the same time as the new buildings were opened. In late 2009, a new Business Studies block, new staff room and atrium were also built.

In 2024 and 2015 the school received an Ofsted rating of Grade 2 "Good", following a previous rating of a Grade 1 "Outstanding" in 2011, and "Good" in 2007. The school converted to academy status on 1 February 2013.

In 2006, the school was granted Specialist Status as a Languages and Engineering College. It became the first school in Lincolnshire to gain joint specialist status in these subjects. Accompanying the specialist status was building work to improve general aspects of the school, and to provide a Language Lab and Engineering Lab for the teaching of the subjects. The school converted to academy status on 1 February 2013.

• Maurice Johnson (antiquary) (c.1700–5)
• William Hobson Mills, organic chemist who investigated stereochemistry and found the Mills-Nixon effect
• Harrison Burrows - Professional footballer for Peterborough United
• Will Wand - Professional rugby player for Leicester Tigers
• Stuart Storey - British sports commentator and former 110m hurdler

• Spalding High School - Selective all girls school, but accepts boys into their sixth form.

• Spalding Grammar School
• EduBase