McCartney II is the fourth solo studio album by the English musician Paul McCartney, released on 16 May 1980. It was recorded by McCartney at his home studio in the summer of 1979, shortly before the dissolution of his band Wings in 1981. Like his debut solo studio album, McCartney (1970), he performed all the instruments himself. It yielded three singles: "Coming Up", "Waterfalls", and "Temporary Secretary".

The album was a significant departure for McCartney, as much of it relies heavily on synthesisers and studio experimentation, while its music style embraces new wave and elements of electronica. It was initially released to largely unfavourable reviews by critics, though retrospective reception has been more positive and the album has become a cult favourite. In 2011, an expanded edition of McCartney II was issued with over a dozen bonus tracks. In 2020, the album was succeeded by McCartney III. In 2022, the trilogy was reissued in the McCartney I II III box set.

After the release of what turned out to be Wings' final album, Back to the Egg, McCartney went north to his farm in Scotland to begin some private recordings in July 1979. "Check My Machine" samples dialogue from the 1957 Merrie Melodies cartoon featuring Tweety and Sylvester entitled Tweet Zoo. By sessions' end, he had recorded over 20 songs. With no immediate use for the recordings, he put them aside for the time being and returned to work with Wings to prepare for a UK tour that November and December.

Simultaneously with the performances (which included the new "Coming Up"), McCartney released his first solo single since 1971, the Christmas-themed "Wonderful Christmastime", backed with "Rudolph the Red-Nosed Reggae", which charted at No. 6 in the UK but initially only at No. 83 in the US. (The song later reached No. 28 in 2020.) The A-side was recorded during the McCartney II sessions, while its flip side had been cut in 1975. However, upcoming events were about to change McCartney's plans with Wings.

After years of visa refusals due to his past arrests for marijuana possession, Japan had finally allowed McCartney, and thus Wings, to perform. It would be the first instance McCartney had performed in the country since he had done so with the Beatles in 1966, and anticipation was running high with Wings' tour completely sold out. However, upon his arrival in Tokyo on 16 January 1980, a search of McCartney's luggage revealed a bag containing 219 grams of marijuana, prompting his immediate arrest and eventually cancelling the tour. After a nine-day jail stay, McCartney was released and returned home to his Scottish farm. Deciding to put Wings on hold while he contemplated his future, he now decided to issue his solo recordings from the previous summer.

McCartney II was named in follow-up to his debut album McCartney (1970) because McCartney plays all instruments on both albums; he has also since stated that he had specifically hired a 16-track machine and "a couple of microphones" with which to record this album, adding that he had himself alternately played the drums used in several recording in either the kitchen or bathroom in order to achieve the echo he sought on particular songs.

Featuring arrangements that are heavy on synthesisers, McCartney II has been said to represent McCartney's "acceptance of new wave", and has been described as "airless proto-electronica". The album is often experimental, with most of its songs having been described as strange "eccentric synthpop". Although McCartney denies any direct influences on the album, he admired the "eccentricity" and "not-mainstream attitude" of Talking Heads' David Byrne. McCartney was also inspired by experimental composers John Cage, Cornelius Cardew and Luciano Berio; McCartney explained: "I went to their concerts in London because I had plenty of time on my hands so it was the kind of thing I would go and see. Again, just to see what it was about, not necessarily because I was a massive fan. It was more like: what is a prepared piano? Oh, that's what it is. You know, funky stuff like that."

According to Stephen Dalton of The Quietus, parts of the album are reminiscent of krautrock and "the whole post-punk disco boom", and described most of the album as "an alluringly weird mash-up of trip-hop, Krautrock and synth-pop." McCartney said that, "rather than me emulating anyone, it was more a question of me seeing what I could do with it. And again, not necessarily thinking I was making an album, just to have some time to experiment. These days I would say that with The Fireman project. So I've always been into that – if you go from 'Tomorrow Never Knows' through McCartney I, McCartney II, The Fireman…" Many of the most synthesised tracks are instrumentals which have been described as ambient; journalist Stephen Thomas Erlewine compared them "to a sprightly variation" of the instrumentals from the second side of Low (1977) by David Bowie, albeit with a warmer, less menacing sound. The instrumental "Frozen Jap" came about as McCartney was experimenting with synths and stumbled upon, in his words, an "Oriental"-sounding melody. The title was meant to be a placeholder as McCartney found earlier song names like "Crystalline Icicles Overhang the Little Cabin By the Ice-Capped Mount Fuji" and "Snow Scene in the Orient" to sound clumsy. On Japanese copies of the album, the title was changed to "Frozen Japanese" because McCartney was unaware that "jap" was seen as a racial slur.