As it appears in the lore, Gwen is about 1030 ~ 1045 years old starting from when she’s been sewn by Isolde. Her human form however seems to indicate an age between 18 and 25 even though it has only been a couple of years since she’s been transformed from her doll body to a girl’s.
We’ll do a chronological analysis of Gwen’s age based on the Noxian calendar, a standard in the world of Runeterra. It pinpoints the year 0 as the foundation of Noxus with BN and AN corresponding respectively to Before Noxus and After Noxus (pretty similar to BC and AC in the Georgian calendar).
With that being said, we can now make informed observations about Gwen’s age using Key events in her storyline as reference:
In the 2021 game Ruined King (which is confirmed by Riot to be canon), A doll of Gwen can be seen in a specific section, indicating that she transformed into her Human form around the timeframe in which Ruined King is set, which is 997 AN. And since we’re currently in 1000 AN this makes Gwen roughly 3 years old.
This isn’t the full story though as one could argue that, since she can remember events from her village in Camavore, and her witnessing the events of the Ruination (which happened in 25 BN), we would consider Gwen as alive even in her doll form, which makes her around 1040 years old!
"Viego. You never deserved love. Especially not hers." -Gwen
It should be noted that this is a rough estimate since we don’t have an exact year when Isolde made her, and since she was born around 70 BN it’s safe to assume that she made Gwen in her 20s or 30s.
A magical doll brought to life by the fragments of Isolde’s Soul (Viego’s wife), Gwen is a joyful girl cherishing her newfound humanity and embracing the love given by her seamstress creator.
Armed by the Scissors, needle and thread that once made her, and accompanied by the wretched souls of the Hollowed Mist, she clenches to the few slivers of good left in a broken world, fighting to save hope that was once lost to her.
In the far kingdom of the now-lost lands of Camavor, Gwen was once created as a doll by a seamstress named Isolde, who infused her with a spirit of joy and adventure. For years, Gwen lived in the warm embrace of her maker who gave her all the care she had.
This would all change when Viego, the King of Camavor, approached Isolde, marrying her and drawing her more distant from Gwen day after day. And when Isolde succumbed to illness from an assassin’s dagger, Viego attempted to resurrect her lifeless body in the Blessed Isles, this however would unleash the Ruination upon Runeterra, giving birth to the shadow isles and abandoning Gwen for centuries.
Following Miss Fortune’s mission with her crew to take down Viego, Isolde’s soul escaped the amulet in which she was imprisoned, and a fragment of hers possessed doll Gwen, transforming her into a human and empowering the tools that once made her with magical powers to control the Shadow Isles’ Hallowed mist.
And now, equipped with magic and freshly acquired life, Gwen would seek to purge the world from the suffering brought by Viego and dispel the Black mist awoken by the Ruination.
