St George, as a military martyr saint has, not surprisingly, become the patron of several chivalric orders.
The most famous is, of course, the Order of the Garter, founded in 1348 by King Edward III. There is a history here, and this is what the present Sovereign's website says about it.
In Russia there is the Order of St George, founded by the Empress Catherine II in 1769. The distinctive riband design survived for a military decoration even in the Soviet era, and the Order was re-established in 1994.There are details and pictures of the insignia here.
Earlier in origin even than the Garter is the Hungarian Order of St George. A chivalric guild under the patronage of King Charles I it originated in 1326, but appears to have had a rather discontinuous history, but has been revived again in recent years, and functions as a charitable foundation. Its British website is here, and for those of you who are less acquainted with the life of Charles I, (sometimes referred to as Charles Robert or Carobert) there is an account of him here.
The Kingdom of the Two Sicilies has the Constantinian Order of St George. This also functions - is its disparate forms - as a charitable foundation. Its history is given here.The website of the branch, under H.R.H. the Duke of Castro, and which operates in Britain, is here.
Like the claim to the throne of the Two Sicilies the headship of the Order is divided between rival claimants, three in the case of the Order, as opposed to two in respect of the throne itself. Considering at the history of Il Regno one should not be surprised. I can see that acquiring a reasonable understanding of the issues, claims and personalities in the current dispute could, quite apart from its genuine interest, also be socially very useful as either a conversation starter or killer depending on the circumstances in which one found oneself.
In addition the Kingdom also had the Order of St George and Reunion. This was founded in 1819 by King Ferdinand I ( formerly Ferdinand IV ) to celebrate the creation of the United Kingdom of the Two Sicilies three years previously. Details of this Order can be found here.