This is a posable action figure from the Nendoroid series.
From the Good Smile Company website:
From the popular smartphone game "Fate/Grand Order" comes a Nendoroid of the Saber class servant, Arthur Pendragon (Prototype)! He comes with three face plates including a handsome standard expression, a heroic shouting expression as well as a slightly more bashful blushing expression.
His sword Excalibur with all of its beautiful details is included for him to wield, allowing for various different poses from the game! Enjoy your very own knight in shining armor shrunk down to adorable Nendoroid size!
Also Available: Nendoroid Saber/Arthur Pendragon (Prototype): Ascension Ver.