Finnish startup Ourahas closed its Series D funding round at $200mn, bringing the smart ring makers valuation to a cosy $5.2bn.Ouras smart ring uses 20 biometric markers to track sleep, physical activity, and stress resilience. The device displays this data on an app that gives you a personalised readiness score. We tested the wearable earlier this year and were genuinely impressed.Founded in 2013, Ourasecured its first funding on Kickstarter, the crowdfunding site, in 2016. Counting this new tranche of capital, the tech startup has raised $550mn since inception.Weve made significant progress in advancing our mission to make health a daily practice and will use this funding to unlock new opportunities, with AI development at the centre of our strategy, said Tom Hale, Ouras CEO.Read the case studyIn 2022, Ourabecame a unicorn and sold its millionth ring. Two years on, the company claims to have recently sold its 2.5 millionth device and to have made $500mn in sales this year alone.We know that Ourahas the potential to change lives at scale, and were excited to continue leading the market in innovation while pursuing opportunities that extend beyond the ring, said Hale.Oura said it signed partnerships with key retailers such as Amazon and Target this year. The ring is especially popular with celebrities including Prince Harry, Gwyneth Paltrow, and Jennifer Aniston. Even the Pentagon made a $96mn order in October to put the devices in (or should I say on) the hands of soldiers.While sales of smartwatches flatlined this year, smart rings are surging in popularity. Global smart ring sales are set to almost double from an estimated 1.7mn by the end of 2024 to 3.2mn in 2028, market intelligence firm IDC. For many users, theyre seen as a more convenient option to smartwatches like the AppleWatch but still contain many of the same features. Smart rings also tend to move less and fit better against the skin.Smart ring makers sold 880,000 units in 2023, said IDC. The OuraRing made up 80% of these sales, soaring above competitors like Ultrahuman and Samsung. By those figures, Oura genuinely does seem to be the current lord of the (smart) rings. Sorry, I couldnt help myself.Fidelity Management led the funding round, which also saw the participation of Dexcom, a German provider of glucose monitoring sensors for diabetes patients. Story by Sin Geschwindt Sin is a climate and energy reporter at TNW. From nuclear fusion to escooters, he covers the length and breadth of Europe's clean tech ecos (show all) Sin is a climate and energy reporter at TNW. From nuclear fusion to escooters, he covers the length and breadth of Europe's clean tech ecosystem. He's happiest sourcing a scoop, investigating the impact of emerging technologies, and even putting them to the test. Sin has five years journalism experience and holds a dual degree in media and environmental science from the University of Cape Town, South Africa. Get the TNW newsletterGet the most important tech news in your inbox each week.