The Alexandra, in Wimbledon, has said there are no strings attached and people who have never been in the pub before are welcome.
A statement on the pub's Facebook read: "I've been asked by a few people now if we are doing the 'free meal for anyone who is on their own' thing on Christmas day this year. The answer is that of course we are, and we're doing it exactly the same as last year.
"There's no tricks, hidden marketing swerves or strings, it's quite simple. If you are going to be on your own for whatever reason on Christmas day, come over and we'll give you a Christmas dinner and pint/glass of wine for free.
"Free means free, once you've eaten it and drank it you can toddle off home if you want, you are not obligated one per cent to buy anything at all. We don't want your email address, it doesn't matter if you never set foot in the pub again and never came here before, as long as you leave here happier than you would have been if you hadn't walked in on Christmas day, we've done our bit.
"If you know someone who might be on their own, let 'em know. If you live miles away, consider maybe bobbing round to a neighbour or relatives house near you for 20 minutes at Christmas, have a glass of wine or beer with them and have a laugh. You going round might very well be the highlight of their day. Do something good for somebody this Christmas, it's kind of the whole point when it comes down to it."
The Alexandra's offer is not the only initiative aimed at making sure no one's on their own on Christmas Day. The hashtag #joinin, publicised by the comedian Sarah Millican, aims to connect people who might otherwise be alone over the holidays so they can chat on social media.
Some posters have been using the hashtag to offer places at their own Christmas meals while others are suggesting gift exchanges.
"Anyone on their own want to do a gift exchange? I love buying gifts for people," posted Twitter user Kayleigh.