Soft grunge (or Tumblr grunge) was a fashion trend that originated on Tumblr around the late 2000s and early 2010s. Beginning as an outgrowth of the 2000s indie sleaze fashion trend but with a greater influence from the 1990s, particularly grunge fashion, the style began as a reaction against the glamor fitness culture which was dominant in popular culture at the time. It is characterized by its merger of cute and aggressive fashion hallmarks like chokers, tennis skirts, leather jackets and boots, flower crowns, distressed denim and pastel colors. Soft grunge reached its peak popularity around 2014, by which time it had been embraced by high fashion designers including Hedi Slimane and Jeremy Scott and been worn by celebrities including Charli XCX. Its internet-based merger of subculture, fashion and music made it one of the earliest examples of an internet aesthetic. In the early 2020s, the style experienced a minor resurgence due to videos posted on the video sharing application TikTok.

By the 2000s, indie sleaze fashion had become popular, which including traits of 1970s and 1980s fashion in addition to grunge and the contemporary hipster fashion. Soft grunge evolved directly from this trend, once Tumblr users began to merge it with darker fashion elements like fishnets, chokers and combat boots. A 2022 article published by i-D specifically cited Hope Sandoval's incorporation of baby tees, slip dresses and mesh as influential upon the development of soft grunge. Teen Vogue writer Kara K. Nesvig and Refinery29 writer Sadhbh O'Sullivan also cited emo fashion as a notable component. Early on its development, the style was deliberately confrontational to the fitness culture which was dominant in popular culture at the time, namely Victoria's Secret's Train Like an Angel campaign and online fitness influencers like Blogilates and Freelee the Bananagirl.

Alternative Press writer Marian Phillips cited Sky Ferreira as having "largely popularized" the style beginning in 2009. Ferreira's style was a direct outgrowth of indie sleaze, making use of chunky boots, babydoll dresses, leopard print, leather, tennis skirts, smudged makeup and grown out dark roots on bleached blonde hair. In a 2014 article for Vogue, stylist Ian Bradley called Ferreira's look "A mix of sexy, innocent and tough". Nylon specifically cited the music video for her song "Everything Is Embarrassing" (2012) as the "utmost style inspiration" on Tumblr. In the following years, musician Lana Del Rey, models Kate Moss and Kylie Jenner and actress Kaya Scodelario's portrayal of the fiction character Effy Stonem, all became points of inspiration for the emerging fashion style.

The style was soon embraced by the fashion mainstream, with Jeremy Scott using its influence for his fall 2012 collection for luxury fashion house Moschino, and in 2013 Ferreira becoming Hedi Slimane's muse when he took over as the creative director for luxury fashion house Yves Saint Laurent. Following the release of her 2013 debut album True Romance, Charli XCX emerged as an influence on the style, appearing at the NME Awards in a soft grunge that included tartan mini skirt, fishnets, crop top and smudged makeup. By 2015, "grunge" was Tumblr's most reblogged fashion term, with soft grunge and pale grunge both appearing in the top 20.

i-D magazine called the style one of the earliest internet aesthetics which become commonplace by the 2020s. In addition to this, the website cited the style as influential on both the e-girl and VSCO girl fashion styles, which originated in the late 2010s. The style was also influential on 2020s rockstar girlfriend, ballerina sleaze and coquette trends.

Around 2022, the style began to experience a resurgence in popularity due to videos uploaded on the video sharing application TikTok, where by August of that year, the hashtags 2014Tumblr accumulated 232 million uses, GrungeAesthetic with 611 million uses and TumblrAesthetic with 46.6 million. Harper's Bazaar's writer Ella Sangster credited the revival as a reaction against the clean girl aesthetic which had been prominent on the same platform since 2020. The same year, luxury fashion house Ports 1961 launched their fall/winter 2022 campagne which featured models Vittoria Ceretti and Bella Hadid in soft grunge inspired outfits taken on polaroid cameras. During this time, the style was embraced by celebrities including Emma Chamberlain, Doja Cat and Olivia Rodrigo.

Soft grunge was based upon the dominant fashion silhouette of the 2010s: high-waisted, tight-fitting trousers or pleated mini skirts with crop tops or t-shirts; while also making use of items common in the 1990s. One of the key aspects of the style is its merger of edgy and distressed "grunge" items with traditionally beautiful "soft" motifs like the colour pink, hearts and nostalgia. Racked media writer Frank Gargione called the style a take on grunge fashion but "commoditized by chain stores and available in softer, sweeter colors".

Soft grunge outfits often include: the usage of studs and spikes, Vans skate shoes, band shirts, Dr. Martens shoes and boots, tennis skirts, chokers, flannel shirts,