Sherlock was the most watched programme over the festive period with 11.6 million viewers.
In the overnight ratings, an average of 9.2 million tuned in to see the case of The Abominable Bride solved by Benedict Cumberbatch as Sherlock Holmes and Martin Freeman as Doctor John Watson.
In addition to appearing in the present day, the world's most famous consulting detective and his best friend were transported to a Baker Street of steam trains, hansom cabs and top hats in 1895.
However, the BBC One show added over two million via catch-up and on demand services, according to consolidated viewing data issued today by the Broadcasters' Audience Research Board (Barb).
After Sherlock, the next biggest programme of the festive season was the New Year's Eve London fireworks display, which had a consolidated audience of 11.4 million.
The Abominable Bride is the second most watched Sherlock episode ever. Top spot goes to The Empty Hearse, the third series 2014 premiere which achieved a consolidated audience of 12.7 million.
At 40.2%, The Abominable Bride also had the highest ever share of the audience for a Sherlock episode.
Sue Vertue, producer of Sherlock, said: "We are thrilled to be a hit in both 2016 and 1895."
Charlotte Moore, Controller BBC One, added: "After a two-year wait, it's incredible to see the indisputable power of Sherlock bringing the nation together to make it the biggest show of the festive season.
"It's a tribute to the talented team behind this much loved show."
Written and created by Steven Moffat and Mark Gatiss, and inspired by the works of Sir Arthur Conan Doyle, Sherlock also enjoyed a huge audience at the box office in China where it has been released in cinemas.
It grossed 5.39 million dollars in its first day, according to figures from Ent Group.