Celtic got the better of Hearts 2-1 at Hampden Park in Glasgow in the final of the Scottish Cup.
The win means that the Hoops have clinched the domestic treble for the third season in a row.
Liverpool left-back Robertson has taken to Twitter to congratulate Celtic on their stunning achievement.
Treble treble winners incredible achievement by @CelticFC— Andrew Robertson (@andrewrobertso5) May 25, 2019
Robertson is one of the best left-backs in the world and is valued between €70 million (£61.7m) and €90m (£79.33m) by the the CIES Football Observatory.
The 25-year-old Scotland international left-back recently told Liverpool’s official website that he is a Celtic fan.
The youngster was actually released by Celtic when he was a teenager, but now he is one of the best left-backs on the planet and could win a Champions League medal this season.
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