The Los Angeles-based giant has been in London for 20 years but has only practised US law until now.
Gibson Dunn is ranked 14th in the US in terms of gross revenues and has reported profits per partner of $815,000 (u509,375).
Paul Harter, corporate partner at the London office, says: "We believe the premier law firms in the 21st century are going to be those capable of competing effectively for business in both London and New York, and other principal markets.
"We have a broad-based clientele - corporate, banking and others - that has been waiting for us to do this for some time."
The four-partner London office will be taking on partners from City firms to compete for UK work.
Harter adds: "We want to hire top-quality partners in principal practice areas to enable us to be a law firm at the top of the market in the City of London.
"The firm is looking to lure top City partners in M&A, corporate finance, project finance, tax and litigation to compete for UK work."
Harter would not be drawn on timing or numbers for growing the office.
"The key is that we are not going to compromise our quality standards to play a numbers game," he says.
The firm will move from its Pall Mall office into larger premises in the City as it seeks to compete in the square mile.
"The UK lawyers we speak to know more about what it takes to be successful in the City of London, and that's what they are telling us we should do - and we need more space," says Harter.
He says Gibson Dunn will expand its own operations in the UK rather than join the ranks of US firms considering transatlantic mergers.
As well as London, it has 10 US offices and one in Paris. It topped the league for the number of M&A deals in California last year.