The singer made the announcement via his official Instagram account, writing: "Got myself a fiance just before new year".
The two have known each other since they were teenagers.
Ed Sheeran got recently engaged to Cherry Seaborn.
The man cave will connect to his main Sussex home via an underground concealed tunnel and will feature a movie theatre and music room.
Ed announced his engagement to the world yesterday afternoon - less than 30 minutes after I called his team to say I was going to break the story today. "We are very happy and in love, and our cats are chuffed as well xx [sic]".More news: Manchester United must choose between Cristiano Ronaldo or Gareth Bale
Sheeran reportedly had a crush on Seaborn even back then, despite her being in the year below. She previously competed in the British University Ice Hockey Championship in 2012 and 2013.
She has worked in the Wall Street financial district of NY, before finally shifting base to her motherland England.
She is now working as a senior consultant in risk advisory for the global accounting firm Deloitte in London. Swift posted a photo of the couple to her Instagram, which has since been deleted.
In an interview on BBC Radio 2 in February 2017, Sheeran said: "I spent every day for a year with this certain person, we kind of have a strong relationship now, which is good". I feel like when you play a stadium you can not play any bigger than that because what do you do?
There's no word yet on when the pair is getting married.