Shopping centre owner Hammerson, which owns Birmingham's famous Bullring, has agreed a £3.4bn takeover of rival Intu.
The deal will create the UK's biggest property company, worth £21bn.
Intu owns the Lakeside shopping centre, in Essex. and the Trafford Centre, in Manchester, while Hammerson owns Bicester Village designer outlet and London's Brent Cross shopping centre.
Shares in Intu jumped by nearly 19% on the news, while Hammerson's fell by 3%.
The combined group plans to target fast growing markets in Spain and Ireland.
John Strachan, chairman of Intu, said: "Intu offers high-quality retail and leisure destinations in the UK and Spain, which, when merged with Hammerson's own top-quality assets in the UK, in France and in Ireland, present a highly attractive proposition for retailers and shoppers in Europe's leading cities."
Hammerson chairman David Tyler said: "This transaction will deliver real value for shareholders. The financial strength of the enlarged group and its strong leadership team will make it well-placed to take advantage of higher growth opportunities on a pan-European scale."
Hammerson shareholders will own 55% of the combined firm and Intu investors the rest. Shareholders will vote on the deal next year.
The combined group would be led by Hammerson chief executive David Atkins and chaired by Mr Tyler.
Russ Mould, AJ Bell investment director, described Hammerson's takeover of Intu as "dramatic, given how terribly Intu's shares have down this year, amid fears over not just what Brexit may do to consumer confidence but also the fate of bricks-and-mortar retailers at the hands of Amazon and other online rivals".
He said the all-share offer suggested "Hammerson's management think they are picking up a bargain in the form of the owner of the Trafford Centre in Manchester, Lakeside and Gateshead's Metrocentre".
"For all of the gloom surrounding the FTSE 100's real estate investment trusts , they have yet to show any signs of Brexit-related stress. In fact, their net asset values have continued to rise, to confound the sceptics' worst fears," he added.
Analysis: Dominic O'Connell, Today business presenter
The union of Hammerson and Intu – the company formerly known as Capital Shopping Centres – has been the Holy Grail of property investment for more than a decade.
The relative underperformance on Intu shares, which have at times traded at a discount to book value as high as 50%, has brought an opportunity for David Atkins, Hammerson's ambitious chief executive.
The other key factor was the willingness of John Whittaker, the secretive billionaire who was the big shareholder in Intu, to come to the table.
The end result is a shopping centre monster – £21bn worth of assets across Europe – that will quickly weed out underperforming properties once the deal is done.