The Open, staged by the R&A, is held on links golf courses throughout the United Kingdom. In 2019, that includes Northern Ireland once again. The small country hasn't hosted The Open since 1951, but Royal Portrush is back and better than ever with new holes created.
The Open was originally staged at Prestwick Golf Club in 1860, then just a 12-hole course. Prestwick held every Open thru 1873, and last hosted the event in 1925.
The Old Course in St. Andrews was the first event outside of Prestwick to host the Open in 1873. It is the most regular host these days, hosting the event generally every five years. That five-year streak (since 1990) was broken in 2020, but it is expected (but not formally announced) to host the 150th staging of The Open in 2021.
Future venues to keep an eye on begin with the Ailsa Course at Trump Turnberry, a famous host for both the Duel in the Sun as well as Tom Watson's near-miraculous victory in 2009. It is questionable whether the R&A wants to stage an Open there while owner of the resort, President Donald Trump, remains in office. The Honourable Company of Edinburgh Golfers, who own Muirfield, voted in 2017 to allow women members. That vote was reportedly required in order to keep Muirfield in the present-day rota.
Four clubs have hosted the Open that are not in consideration at the time for future opens. Prestwick, Musselburgh Golf Links, Royal Cinque Golf Club and Prince's Golf Club are all some combination of too short or logistically challenging for future events. All 14 courses that have held The Open are open to the public.
Future venues announced by the R&A for The Open
2018 Open Championship
Carnoustie Golf Links, Championship Course, Angus, Scotland
Past Opens: 1931, 1937, 1953, 1968, 1975, 1999, 2007
2019 Open Championship
Royal Portrush, County Antrim, Ireland
Past Opens: 1951
2020 Open Championship
Royal St. George's, Kent, England
Past Opens: 1894, 1899, 1904, 1911, 1922, 1928, 1934, 1938, 1949, 1981, 1985, 1993, 2003, 2011