Garter Day constitutes the most significant annual assembly of the Most Noble Order of the Garter, the senior order of British knighthood established by Edward III in 1348. The day is marked by a private investiture of new companions in the Garter Throne Room of Windsor Castle, followed by a state luncheon and a grand procession of the Sovereign, the Royal Family, and the Knights and Ladies Companion. Clad in velvet mantles, plumed hats, and the collar of the Order, the participants process to St George's Chapel for a service of thanksgiving, accompanied by the Officers of Arms and the Military Knights of Windsor.
The ceremony serves as a visual manifestation of the bond between the Crown and its most distinguished subjects, blending medieval chivalry with modern constitutional stability. Historically, the day was aligned with the Feast of Saint George (April 23rd), but since the mid-20th century, the 'Garter Monday' of June has become the standardized date. It remains a rare occasion where the full college of Heralds—led by Garter King of Arms—appears in state dress to perform their traditional ritual functions, underscoring the enduring relevance of heraldic hierarchy in the British honors system.