The Portuguese defender has been outstanding since joining City in September and has become an integral member of the first team squad.
City conceded just three goals in November and Dias has been one of the main reasons that we have conceded the joint-second fewest goals in the Premier League this season.
John Stones narrowly missed out on the prize with Joao Cancelo also polling many votes in one of the closest player of the month contests yet.
Thanks to everyone who voted and congratulations to Ruben.
We will have full coverage of the Manchester Derby right here on ManCity.com.
Our Matchday Centre will get under way at 3.30pm, with text updates throughout the day meaning you won't miss a beat.
Our We're Not Really Here live matchday show starts at 4.30pm, with Shaun Goater and Gareth Barry and Michael Brown joining us in the studio.
And CITY+ subscribers can enjoy a full 90-minute replay from midnight.
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