Sanchez netted his latest treble in the 5-2 win over Leicester City on Saturday - his first Premier League hat-trick since joining the Gunners from Barcelona last summer.
The Chile international also scored league hat-tricks for both Barcelona and Italian side Udinese.
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Noting the impressive achievement, Arsenal created a special infographic for the South American, alongside the caption: "Congratulations, @Alexis_Sanchez!".
Needless to say, the tweet went down with the Arsenal faithful - and you can see some of the best replies by scrolling down this page.
Arsenal fans react on Twitter
Sanchez needed proper rest after Copa America
It was always likely to take Sanchez a little bit of time to rediscover his best form at the start of this season following his exploits at the Copa America in the summer.
The 26-year-old helped Chile end their 99-year wait for the prestigious South American trophy, scoring a Panenka penalty in the final against Argentina.
There was little time for Sanchez to rest, however. Arsene Wenger may have allowed the world-class attacker to miss the Community Shield against Chelsea, but less than a week later he was used as a second-half substitute in the opening-weekend defeat to West Ham.
It was too early for Sanchez who, by his own standards, was below-par for the next few weeks.
But he's back in business now and back among the goals.
Arsenal fans: is Alexis Sanchez your best player? Have your say by leaving a comment in the box below!