Mermaidcore is a fashion and lifestyle microtrend popularized on social media platforms like TikTok and Pinterest in the early 2020s. It is inspired by the mythology and visual representation of mermaids, sirens, and other aquatic life. The aesthetic is defined by a color palette of oceanic blues, greens, and lilacs; iridescent and shimmering fabrics that mimic fish scales; and motifs such as seashells, pearls, and coral.

The aesthetic draws on escapist fantasies of a magical life under the sea, blending elements of nostalgia from Y2K -era media with modern high-fashion interpretations. It encompasses a range of styles from whimsical and romantic to a darker, more menacing "telchine" look.

While mermaid-inspired fashion has a long history, including the mermaid-silhouette gown created by French couturier Marcel Rochas in the 1930s, the modern Mermaidcore aesthetic is an internet-native phenomenon. Its visual canon is heavily influenced by nostalgic media from the early 2000s, such as the film Aquamarine (2006) and the television series H₂O: Just Add Water , which are frequently cited as inspirations by adherents of the trend.

The aesthetic began to gain traction on the runways in the post-pandemic era, with designers incorporating oceanic themes into their collections. Versace's Spring/Summer 2021 collection featured dresses printed with seashells and starfish, which is often cited as an early example of the trend's high-fashion emergence. By 2023, the trend had reached its peak, driven by the cultural impact of Disney's live-action The Little Mermaid . This was reflected in online engagement, with the hashtag #mermaidcore amassing over 14.5 billion views on TikTok, and Pinterest reporting a 614 percent increase in searches for the term.

Mermaidcore fashion is characterized by its use of fabrics, textures, and silhouettes that evoke the sea. Iridescent materials, sequins, and large, shimmering paillettes are used to create the effect of fish scales on gowns, tops, and skirts. Flowing and sheer fabrics like tulle, organza, and chiffon are chosen to mimic the movement of water, while net-like materials such as crochet and fishnet are also common. Key garments include shimmery bralettes and corsets, sheer or ruffled maxi skirts, and elegant mermaid-silhouette gowns that are fitted through the body and flare out at the knee.

The color palette is central to the aesthetic, drawing from deep-sea blues, aquamarine, seafoam green, and jewel tones like sapphire and amethyst. These are often accented with pastel lilacs, purples, and sunset hues. Accessories are crucial for completing the look, with a focus on jewelry made from natural elements like seashells, pearls, and sea glass. Shell-strung necklaces and belts, pearl earrings, and elaborate, baroque-style headpieces are prominent. The trend has been widely interpreted on the runway by designers such as David Koma, Blumarine, and Louis Vuitton, who have incorporated sequined skirts, shell embellishments, and aquatic prints into their collections.

The beauty standards of Mermaidcore aim for an ethereal, "just emerged from the water" appearance. The "wet look," achieved with high-shine products, is popular for both skin and hair. Makeup often features glossy lips and a heavy use of glimmering, iridescent eyeshadow in shades of blue, green, and purple. This is frequently embellished with glitter, face gems, and pearl-like adornments. A popular technique involves using fishnet tights as a stencil to apply powder highlighter or eyeshadow to the face, creating a realistic scale pattern.

Hair is typically styled to look effortless and flowing. Long, loose "beachy waves," tousled braids, or sleek, wet-look styles are common choices to complement the aquatic theme.