|"Gwendolyne" Julio Iglesias (1970, Colombia) Image: Discogs|
I've been asked this question now and then and to be perfectly honest, the 78 RPM speed is still with us. Mostly for collectors items and not as general releases. But it does occasionally surface.
But as general releases, 78 RPM was largely passe in America by 1957. In 1957, sales of 78 RPM records accounted for 4,500,000 units in 1957. In 1958, it plummeted to less than 500,000, less than 5% of overall sales and the writing was on the wall.
|"Fannie Mae" Buster Brown (1959) This is considered one of the last commercial American pop singles released at 78 RPM. Image: 45 Worlds. However, there were some 78s pressed on budget labels and independents well into the early 1960s .|
|Phonola Record Player, 1950s -60s Note the case is pure Vanity Fair/Imperial Party Time, but the tone arm is a plastic gramophone reproducer that used steel needles. These players (which also sold under Woolworth's house brand, Audition) had two speeds, 45 and 78 (which were the speeds of most kids records available at that time, 45 by the 1970s, but many 78s from the '50s and '60s. still existed.) These players were sold well into the early 1970s. Image: Etsyspot|
|"Jolie" Latimore (1973, Brazil) Image: Discogs|
Here's one from the Soviet Union, circa 1979.
|"September Song" Ian McCulloch (1984, UK) An unusual offering from Ian McCulloch, New Wave legend and frontman of Echo & The Bunnymen, best known for their hit "The Killing Moon", The flip side had a longer version of "September Song" and "Molly Malone (Cockles and Mussels)" and played at 45 RPM. Image: Discogs|
|"You're The One For Me, Fatty" Morrissey (1992, UK) Image: Discogs. Morrissey was the former lead singer of the British pop group The Smiths, best known for their 1984 alternative rock mega hit "How Soon Is Now". In 1992, he released a few 78s with selections from his solo album Your Arsenal.|
|"Millennium" Robbie Williams (2000, UK) Limited Edition of 999 numbered copies issued to commemorate the opening of the new HMV store in Oxford Street, London. Image: Discogs|
So to sum up, the last official general release new Western pop single on 78 that isn't a reissue, novelty, oddity, collector's item or promo is one that may never truly be known, even among collectors and they're still searching. The 1973 Brazilian Latimore 78 mentioned above is the most recent I've seen yet. I have heard of others that extend into the disco era, but I've never seen any as of this writing.
|"Terraplane Blues" Robert Johnson (2019 Record Store Day reissue) Image: Discogs|