Hong Kong Exchanges and Clearing has launched a bid for the London Stock Exchange Group.
It said the move to merge the two companies would create a "global market infrastructure leader".
HKEX's cash-and-shares proposal would see it pay around £8.36 a share for LSE - which values it at around £29.6 billion or £31.6 billion including debt.
HKEX said: "The proposed combination would strengthen both businesses, better position them to innovate across markets and geographies, and offer market participants and investors unprecedented global market connectivity."
HKEX chairman Laura Cha said: "We believe a combination of HKEX and LSE represents a highly compelling strategic opportunity to create a global market infrastructure group, bringing together the largest and most significant financial centres in Asia and Europe.
"Following early engagement with LSE, we look forward to working in detail with the LSE board to demonstrate that this transaction is in the best interests of all stakeholders, investors and both businesses."
It's not the first time HKEX has cast its eyes to London, having bought the London Metal Exchange in 2012.
HKEX chief executive Charles Li said: "Bringing HKEX and LSE together will redefine global capital markets for decades to come.
"Both businesses have great brands, financial strength and proven growth track records. Together, we will connect East and West, be more diversified and we will be able to offer customers greater innovation, risk management and trading opportunities.
"A combined group will be strongly placed to benefit from the dynamic and evolving macroeconomic landscape, whilst enhancing the long-term resilience and relevance of London and Hong Kong as global financial centres."
