ICAP said it would be known as NEX Group PLC following the deal to sell its global broking business to Tullett, which is expected to take place before the end of 2016.
Former Conservative Party treasurer Michael Spencer founded ICAP 30 years ago.
Spencer said: “NEX Group plc will be a fast-moving, entrepreneurial pure electronic and post-trade leader, well positioned for growth.
“We wanted a name to truly reflect this and which was truly global. NEX Group does this. I am very excited about our new name.”
Existing Tullett Prebon shareholders would continue to own 44% of the group after the deal, which is expected to result in savings of at least £60mln.
ICAP said on Monday that group revenue in the year to March 31 had fallen 6% as markets stayed challenging.
Trading pre-tax profit dropped to £203mln from £229mln a year ago due to £7mln of foreign exchange losses.
The group proposed a final dividend payment of 15.4p per share, meaning a flat full-year dividend of 22p per share.
Shares in ICAP dropped 1.1% to 454.1p in early London trading.