Step Back in Time: The Definitive Collection is a greatest hits album by Australian singer Kylie Minogue. It was released on various formats on 28 June 2019 by BMG Rights Management, serving as her first compilation with the label. Minogue confirmed the record in May 2019, after teasing initial content on social media and her website. The album's original content includes forty-two songs, dating back to Minogue's debut with PWL in 1987. In addition, an expanded version included another disc with eight additional tracks from her catalogue, as well as a megamix of various tracks from her career.

Step Back in Time: The Definitive Collection received positive reviews from music critics, who praised Minogue's extensive catalogue, with minor criticism directed at omitted content and packaging. The album was a commercial success, debuting at number one in both Australia and the United Kingdom, where it was certified gold in the latter. The record also reached the top ten in Spain, Belgium, and Switzerland, as well as component charts in the United States. Minogue promoted the album with the single "New York City" and embarked on a tour in mid-2019 throughout Europe, the Middle East, and South America.

Near the end of April 2019, Minogue hinted at a greatest hits release by sharing content from her music video for "Step Back in Time" on social media. In addition, a countdown was added to her official website, which was set to end on May 3, but finished a day earlier. Following the countdown, the website displayed the album's slogan: "Pop Precision Since 1987". She announced the album, Step Back in Time: The Definitive Collection, on her website, with pre-orders available the same day.

The album was planned to coincide with Minogue's 30th career anniversary, as well as her appearances at Glastonbury Festival, Brighton Pride, and other summer festivals that year. It is Minogue's fifth greatest hits collection, after Greatest Hits (1992), Hits + (2000), Ultimate Kylie (2004), and The Best of Kylie Minogue (2012). Its title originates from her 1990 single of the same name, and it is her first compilation release with BMG Rights Management.

The album's original content consists of forty-two songs chosen from Minogue's singing career beginning in 1987; all tracks are arranged in an unchronological order. The first disc includes an unreleased track titled "New York City", which was recorded during the sessions for Minogue's fourteenth studio album Golden (2018). The song "Breathe" appears on disc one between "2 Hearts" and "Red Blooded Woman" on the deluxe edition, whereas "New York City" appears as the final song on disc two as a hidden track. This track order is also followed by the cassette and digital versions of the original release, with the exception of "New York City". Some tracks from Minogue's discography were omitted from the album's original release, which sparked criticism; as a result, a third disc contains eight additional songs from her catalogue, as well as a megamix of Minogue's work lasting more than 40 minutes.

Step Back in Time: The Definitive Collection was released on various formats on 28 June 2019 by BMG Rights Management. The album was released in two standard formats: digipack and 32-page hardcover book, both of which included two discs containing the album's material. Three vinyl sets were released in various colours: black, mint, and picture disc. All vinyl formats contain only twenty of the original album's forty-two tracks, but each copy also included a digital copy. Five two-set cassette tapes were also released in various colours, including clear, gold, green, pink, and white. In November, BMG added additional content to the album; the expanded version was released as a three-disc digipak and digitally on Minogue's website.

Step Back in Time: The Definitive Collection garnered positive reviews from music critics. Tim Sendra of AllMusic gave the greatest hits album four stars, calling it a "fitting tribute" in time for Minogue's 30th career anniversary. Sendra described it as "truly definitive and essential" and concluded by saying "This collection shows just how often that happened, especially after she was able to gain control of her own career." Graham Clark of The Yorkshire Times also awarded the album four stars, stating "In the fickle world of pop Kylie is still there at the top." Mick Jacobs of Spectrum Culture praised the compilation's overall versatility, describing Minogue's dance songs and downtempo moments as having "enduring appeal". Jacobs went on to say, "Step Back in Time stands as a strong reminder of not just how prolific her career has been but also how much more of it we can expect."

However, other critics noted the lack of new material and omitted singles. Classic Pop magazine gave it an 8 out of 10 rating and described it as a "nifty guide to one of the great modern pop careers". However, the reviewer felt it "isn't perfect" or "definitive". Pip Ellwood-Hughes, writing for Entertainment Focus, praised how the album's release "will most likely build on the current wave of love for Kylie that's sweeping the UK". Ellwood-Hughes, on the other hand, called the album's packaging a "disappointment" and concluded that "those of us who've been with her since the start might feel just that little bit underwhelmed with the lack of added extras". Quentin Harrison of Albumism wrote an article echoing similar sentiments about the lack of certain tracks on Step Back in Time, stating that Minogue's singles "Finer Feelings", "Where Is the Feeling?", "Some Kind of Bliss", "Flower", and "Into the Blue" should have been included on the album's original release.