The new commission is Gift Horse by German artist Hans Haacke
Gift Horse, a skeletal sculpture which displays a live feed from the London Stock Exchange, has been unveiled in Trafalgar Square.
The equine bronze, by German artist Hans Haacke, is the tenth artwork to occupy the Square's Fourth Plinth.
London mayor Boris Johnson described the work as "a startlingly original comment on the relationship between art and commerce".
It replaces a giant blue cockerel which was on display for 18 months.
The riderless horse - with an electronic ticker of share prices, displayed on a bow around one of its front legs - is a wry reference to an equestrian statue of William IV originally planned for the plinth, but which never came to fruition due to a lack of funds.
The horse's front leg has an electronic ribbon displaying live the ticker of the London Stock Exchange
Haacke, 78, who is based in New York, was inspired by an engraving in The Anatomy of the Horse (1766) by English painter George Stubbs, whose works are on display in the National Gallery, on Trafalgar Square.
At Thursday's unveiling, Haacke was reluctant to explain what his sculpture was trying to say.
"It is an invitation to make connections," he told the BBC, "but I would not like to give directions. I'm sure there will be a diversity of responses. That is not only true for this but any kind of art."
The sculpture was unveiled by London Mayor Boris Johnson
Boris Johnson said: "There will be those that say this undeniably unfed, emaciated quadruped is a warning, a memento mori, a symbol of the pursuit of austerity and the [Chancellor of the Exchequer] George Osborne diet approach to life.
"But I say no, my friends. This wonderful sculpture stands for the horse in all its incarnations... in these fabulous tubular structures we see symbolised the vital infrastructure - the tube - that must run beneath the surface of any great and beautiful city."
Gift Horse drew positive, if slightly bemused, comments from tourists.
One of the first people to see it was Tim Wright from Lancashire, who told the BBC: "I find it pleasing to look at but I've not a clue what it's trying to say."
