Algonquin Regional High School is a public high school located in Northborough, Massachusetts, United States. The school serves the students of the Northborough-Southborough Regional School District (NSRSD) comprising both Northborough and neighboring Southborough.

The school's mascot as of February 11, 2022, is currently undecided, though the schools teams have a new name "The Titans". The former mascot was the Tomahawk, known by many as the "T-Hawk." On April 28, 2021, the Northborough-Southborough Regional School Committee voted, 9-0, to retire the Tomahawk as its mascot. A study group was assembled to determine a new mascot, which was voted on by the student body at that time. The school's colors are maroon and gold. Algonquin Regional's Superintendent is Greg Martineau and its Principal is Sean Bevan.

In 2003, a $3 million renovation and expansion plan was approved by the district and renovations began that year. Due to failures associated with the general contractor, Eastern Contractors Inc., and need for dismissal of the contractor from the project, delays in completion of the renovation project occurred. In 2005, the regional district fired the contractor from the project. The renovations and expansion efforts were completed as a result of efforts by school district representatives in 2008, with the grand opening taking place on September 4 of that year. In 2023, the high school went through a major renovation of its athletic facilities, referred to as the "Gonkplex" project. The initiative included the installment of two synthetic turf fields. replacing the stadium varsity field and added a new multipurpose field. In addition to the fields, other upgrades include a new running track, ADA-compliant grandstands, and an elevator for the press box. The project will also update the tennis courts, adding pickleball lines, and improve the surrounding grounds. The price for the project was approximately $7.5 million.

Algonquin Regional offers its students a multitude of courses within various disciplines such as Mathematics, Science, Applied Arts & Technology, Fine & Performing Arts, Health & Fitness, Foreign Languages (including Spanish, French, and Latin), and Instructional Support. College Preparatory courses are graded on a 4.0 scale, Honors courses are graded on a 4.5 scale, and Advanced Placement courses are graded on a 5.0 scale.

The following Advanced Placement Courses are offered: AP Microeconomics, AP English Literature and Composition, AP English Language and Composition, AP Studio Art, AP Music Theory, AP Calculus AB, AP Calculus BC, AP Statistics, AP Biology, AP Chemistry, AP Environmental Science, AP Human Geography, AP Psychology, AP United States Government and Politics, AP United States History, AP World History, AP Latin, AP Spanish, AP French, AP Computer Science Principles, AP Computer Science A, AP Physics C, AP Precalculus

The Titans (then Tomahawks) saw considerable athletic success during the early 2000's, winning seven state titles between 2004 and 2012. The Boys' Soccer team won back-to-back titles in 2004 and 2005, and Boys' Baseball followed up with another title for the third straight year in 2006. The Girls' Tennis and Soccer teams both earned state titles in 2009, and the Girls' Gymnastics added two more titles, again back-to-back in 2011 and 2012.

Algonquin maintains a strong cross-town rivalry with Westborough High School, in which both teams compete in an annual Thanksgiving Day Football Game.

The Algonquin Boys' Varsity Soccer team captured two straight MIAA Division I State titles in 2004 and 2005, the first state titles for the entire school. In 2006, they returned to the state final to play St. John's Preparatory School, but lost 4–1.