Parallel Lines is the third studio album by American rock band Blondie, released on September 8, 1978, by Chrysalis Records. An instant critical and commercial success, the album reached No. 1 on the UK Albums Chart in February 1979 and proved to be the band's commercial breakthrough in the United States, where it reached No. 6 on the Billboard 200 in April 1979. In Billboard magazine, Parallel Lines was listed at No. 9 in its top pop albums year-end chart of 1979. The album spawned several successful singles, notably the international hit "Heart of Glass".

"Musically, Blondie were hopelessly horrible when we first began rehearsing for Parallel Lines, and in terms of my attitude they didn't know what had hit them. I basically went in there like Adolf Hitler and said, 'You are going to make a great record, and that means you're going to start playing better.'"

Blondie's second studio album, Plastic Letters (1977), was their last album produced by Richard Gottehrer, whose sound had formed the basis of Blondie's new wave and punk output. During a tour of the west coast of the US in support of Plastic Letters, Blondie encountered Australian producer Mike Chapman in California. Peter Leeds, Blondie's manager, conspired with Chrysalis Records to encourage Chapman to work with Blondie on new music. Drummer Clem Burke recalls feeling enthusiastic about the proposition, believing Chapman could create innovative and eclectic records. However, lead vocalist Debbie Harry was far less enthusiastic about Chapman's involvement as she knew him only by reputation; according to Chapman, her animosity towards him was because "they were New York. [He] was L.A.". Harry's cautiousness abated after she played Chapman early cuts of "Heart of Glass" and "Sunday Girl" and he was impressed.

In June 1978 the band entered the Record Plant in New York to record their third album, and first with Chapman. However, Chapman found the band difficult to work with, remembering them as the worst band he ever worked with in terms of musical ability, although praising Frank Infante as "an amazing guitarist". Sessions with Chris Stein were hampered by his being stoned during recording, and Chapman encouraged him to write songs rather than play guitar. Similarly, according to Chapman, Jimmy Destri would prove himself to be far better at songwriting than as a keyboardist, and Clem Burke had poor timing playing drums. As a result, Chapman spent time improving the band, especially Stein with whom Chapman spent hours rerecording his parts to ensure they were right. Bassist Nigel Harrison became so frustrated with Chapman's drive for perfection that he threw a synthesizer at him during recording. Chapman recalls the atmosphere at the Record Plant in an interview for Sound on Sound:

The Blondies were tough in the studio, real tough. None of them liked each other, except Chris and Debbie, and there was so much animosity. They were really, really juvenile in their approach to life—a classic New York underground rock band—and they didn't give a fuck about anything. They just wanted to have fun and didn't want to work too hard getting it.

Chapman took an unorthodox approach when recording with Harry whom he describes as "a great singer and a great vocal stylist, with a beautifully identifiable voice. However ... also very moody". Chapman was far more cautious of demanding much from Harry as he saw her as a highly emotional person who would vest these emotions in the songs they made. He remembers Harry disappearing into the bathroom in tears for several hours at a time during recording. During a day of recording, Harry sang two lead parts and some harmonies, less work than she did previously with Gottehrer. This was due to Chapman encouraging her to be cautious about the way she sang, particularly to recognise phrasing, timing and attitude.

Blondie recorded Parallel Lines in six weeks, despite being given six months by Terry Ellis, co-founder of Chrysalis Records, to do so. For the drums, a traditional set-up was used and Chapman fitted Neumann microphones to the toms, snare and hi-hat, as well as several above the site. When recording, Chapman would start with the bass track, which was difficult to record at the time, by way of "pencil erasing". Chapman explained in an interview for Sound on Sound, "that meant using a pencil to hold the tape away from the head and erasing up to the kick drum. If a bass part was ahead of the kick, you could erase it so that it sounded like it was on top of the kick. That's very easy to do these days, but back then it was quite a procedure just to get the bottom end sounding nice and tight." A combination DI/amp method was used to record Harrison's bass and Destri's synthesizer. Shure SM57 and AKG 414 microphones were used to capture Infante's Les Paul guitar. King Crimson leader Robert Fripp makes a guest appearance on guitar on "Fade Away and Radiate".

After the basic track was complete, Chapman would record lead and backing vocals with Harry. However, this process was hampered by many songs not being written in time for the vocals to be recorded. "Sunday Girl", "Picture This" and "One Way Or Another" were all unfinished during the rehearsal sessions. When recording vocal parts, Chapman remembers asking Harry if she was ready to sing, only for her to reply "Yeah, just a minute" as she was still writing lyrics down. Chapman notes that many "classic" songs from the album were created this way.