Nathalie Pâque — born 13 May 1977 in Belgium, representing France — performed at the Palais de Beaulieu in Lausanne, Switzerland on 6 May 1989, exactly seven days before her 12th birthday. That makes her, at 11 years and 358 days, the youngest main artist ever to compete in a Eurovision Grand Final. Her song J'ai volé la vie ("I stole life") was a melodramatic French ballad about loss and forgiveness. She finished 8th of 22 entries with 60 points.
The 1989 contest had multiple under-15 performers. Israel sent 12-year-old Gili Netanel as a backing vocalist for Gili and Galit Burg's Derech HaMelech. France's Pâque was the youngest soloist. Both performances became flashpoints for media debate the following Monday.
The rule that followed. The EBU introduced a minimum age requirement of 16 years on the date of the Grand Final, taking effect from Eurovision 1990 onwards. The rule was tightened further in subsequent contests to include all main and backing vocalists. The cumulative effect is that the three youngest performers in Eurovision history (Pâque 11, Netanel 12, Sandra Kim 13) all appeared in a three-year window from 1986 to 1989 — and no performer under 16 has appeared in any Grand Final since.
The youngest post-rule performer. Lucie Jones (UK 2017, Never Give Up on You) was 26 at the contest; she had been 19 when first famous on the UK X Factor in 2009. The youngest verified post-rule Grand Finalist is Junior Eurovision 2010 winner Vladimir Arzumanyan (Armenia, age 12 at JESC) — but JESC is a separate, junior contest and Arzumanyan has not yet competed in the senior Eurovision.
Where Pâque is now. Nathalie Pâque, now in her late 40s, made a low-key adult career in French-language pop before stepping back from music in the early 2000s. She has spoken in occasional interviews about the surreal experience of being 11 years old at a major TV broadcast watched by 600+ million people across Europe. She has not appeared at Eurovision again.