Cristiano Ronaldo teaching his son 'SIIIIUUUUU' celebration is most adorable thing on internet today

Cristiano Ronaldo's trademark 'SIIIUUUU' celebration has been both mocked and admired since his return to Manchester United.

It remains popular among fans for numerous reasons and this footage of him teaching it to his four-year-old son Mateo has gone viral on social media.

Ronaldo says the word to Mateo, who repeats it and the 36-year-old bursts out laughing.

Fans will fondly recall the day Old Trafford went 'SIIIUUUU' during Cristiano's dream second debut this season.

The Portuguese has four children and is expecting twins with long-term partner Georgina Rodriguez.