The Rectified Scottish Rite, also known as the Rectified Rite or rarely RSR, historically known under the RER acronym for Rite écossais rectifié, is a Christian Masonic rite with a long and complex history. It was founded in 1778 at the Convent of Lyon in France under the leadership of Jean-Baptiste Willermoz, who served as the primary architect and driving force behind its formation. It emerged as a reform and restructuring of the earlier Templar Strict Observance system that had spread in Germany and France in the mid-18th century.

The rite is explicitly Christian, requiring candidates to profess faith in Jesus Christ. It incorporates influences and symbolism from branches of esoteric Christianity as well as Masonic Templar movements. The central teachings of the Rectified Scottish Rite focus on the loss and restoration of mankind's original innocence, integrating elements of Martinez de Pasqually's occult Coën theology and Louis-Claude de Saint-Martin's mystical Christianity.

The Rectified Scottish Rite has its origins in the Masonic landscape of 18th century France. Jean-Baptiste Willermoz was a prosperous silk merchant in Lyon who joined the Masonic Order in 1750 at the age of 20. He quickly rose to prominence and by 1763 was the Secretary Keeper of Seals and Archives of the Grand Lodge of Lyon.

In 1767, Willermoz met the mysterious occultist Martinez de Pasqually, who initiated him into his Order of Knight Mason Elect Priests of the Universe. Willermoz became devoted to Pasqually's teachings and Cohen ritual magic system, which sought to achieve communication with angels and restore man's lost divine status. For the next several years, Willermoz operated Rosicrucian study groups and Masonic bodies in Lyon that incorporated Pasqually's rites.

In the early 1770s, Willermoz helped introduce the German Rite of Strict Observance system of Masonic Templarism to France, as part of efforts to revive the legacy of the medieval Knights Templar. He quickly came to believe theStrict Observance degree structure needed reforming and simplification. At a Masonic convention in 1778, he put forth his "Réforme de Lyon" plan to reshape the system into the Rectified Scottish Rite.

The early Rectified Scottish Rite consisted of 4 symbolic lodge degrees, 2 orders of knightly nobility, and a secret "Profession" class at the top incorporating Willermoz's Cohen magical rites and Pasqually's teachings. It also adopted the Strict Observance's system of Masonic provinces to govern the order. The new rite was approved at a national convention in Lyon in 1778 and formally established at the international Convent of Wilhelmsbad in 1782 under Willermoz's leadership.

Over the following decades, Willermoz served as the primary author of the rite's constitutions, regulations, and ritual texts. He gradually crafted the rite's mythology and symbolism to place less emphasis on historical Templar succession and more focus on symbolic Temple rebuilding and restoration of man's original innocence. Christian concepts and theology were made increasingly central.

The Rectified Scottish Rite flourished until the beginning of the French Revolution in 1789. Most Masonic lodges were shut down during the Reign of Terror of 1793–94. While some Rectified lodges survived, the rite declined sharply and failed to recover its former strength.