The Tannadice club confirmed on Wednesday morning that it had agreed an undisclosed transfer fee for the striker, reported to be in the region of £1m, who they signed on a free transfer from Ayr United in 2019.
The 26-year-old Scotland international played 74 times for United, scoring 40 goals, and was a pivotal figure in the club's Championship winning season in 2019-20 before helping them consolidate in the top flight last term.
Shankland said: "I came to United with the objective of developing personally and helping the club get back to the Premiership and I now see it is the right time to take the next step in my career development elsewhere.
“The fans support for me was amazing right from the off and I will always be grateful for their backing and, hopefully, I will be back one day to see them all. I also have to mention the backing I have received from the chairman and vice-chairman who made me feel such a part of this club and welcomed me in so warmly.
"I leave knowing there is an excellent squad and great coaches at United and I am excited to see how successful this season will be for them. I now look forward to my future in Belgium and cannot wait to get started. Thank you to everyone at Dundee United. ”
United decided to cash in on the former Aberdeen and St Mirren striker as he entered the final year of his contract rather than risk losing him for nothing next summer.
Sporting director Tony Asghar said: “Lawrence was sold on the vision we offered both personal and club-wise. He has achieved great success here, became a fans favourite, scored goals, improved his all-round play and became an internationalist. He felt it was time to try something new and once the clubs agreed a fee we were happy to allow him to continue his career elsewhere.
“It is an important part of our strategy that we develop players so they can continue to flourish if they move on and Lawrence has been a great example of the strategy working and we wish him every success for the future. He will always be welcome at Tannadice."
Shankland is due to start training with his new club on Thursday and pending the completion of all the necessary registration paperwork, Beerschot hope he will be eligible to make his debut away to Belgian champions Brugge on Saturday, August 22.
"Lawrence is a prolific goal scorer and that is what Beerschot needs at the moment", technical manager Sander Van Praet said. "He is still only 25-years-old so he can still make progression. He is a real killer in the box. We expect lots of goals from him."
"The type of forward we have been looking for for a while", chairman Francis Vrancken adds. "Lawrence came on our radar through United World and the negotiations have taken quite a bit of time, so, we are relieved and very happy we are now able to welcome him at Beerschot."