The note featuring Boulton and Watt will be introduced in 18 months
Two giants of the industrial age are to appear on a redesigned Bank of England £50 note.
Scottish engineer James Watt and his business partner Matthew Boulton, from Birmingham, developed the steam engine.
Bank of England governor Mervyn King said their 18th Century innovations were essential in driving Britain's Industrial Revolution.
It is the first time two portraits have appeared together on the note. An image of the Queen appears on the other side.
Inventor and mechanical engineer James Watt was born in Greenock in 1736 and carried out some of his first experiments with steam power in Glasgow.
His partnership with Matthew Boulton, who owned the Soho Foundry in Birmingham, gave him access to the latest metal working techniques.
The resulting Boulton and Watt engine proved far more efficient than previous designs, and was soon being used in coal mines and cotton factories.
The new banknote, to be launched in 18 months, includes an image of a steam engine and the Soho factory.
Mervyn King said: "So many of the advantages society now enjoys are due in large part to the vital role of engineering and the brilliance and foresight of people such as Boulton and Watt, whose development and refinement of steam engines gave an incredible boost to the efficiency of industry."
He added: "The unique and rare opportunity that the bank has through its banknotes to acknowledge and promote awareness of our nation's heritage of artistic, social and scientific endeavour is an honour for us.
"The bank's choice of Boulton and Watt, a reminder of the invaluable contribution from engineering and the entrepreneurial spirit to the advancement of society, I think, well reflects this."
The new note will circulate initially in tandem with the existing £50 note featuring the first Bank of England governor Sir John Houblon, but the older note will gradually be withdrawn.