Oxford has slipped from fourth to fifth place
A table of leading world universities shows a fall in the number of North American universities in the top 100 from 42 in 2008 to 36 in 2009.
The sixth Times Higher Education table is based on a survey of academics and graduate employers worldwide.
There are 39 European universities in the top 100, up from 36. The number of Asian universities rose from 14 to 16.
Harvard is still top, while Cambridge moves up from third to second place. Oxford slips from fourth to fifth rank.
University College London jumped up three places from seventh to fourth.
TOP 10 UNIVERSITIES 2009
University College London
Imperial College London*
University of Chicago
Massachusetts Institute of Technology
California Institute of Technology
* = joint place
The University of Tokyo, at 22nd, is the highest ranked Asian university and the University of Hong Kong moved up two places from 26th to 24th.
A new classification in the rankings differentiates between generalist universities and specialist institutions.
Europe does well in this section, with the top specialist social science university being the London School of Economics and the top specialist engineering university being the École normale supérieure in Paris.
Compiling the tables
This year 9,386 academics (compared with 6,354 in 2008) and 3,281 employers (compared with 2,339 in 2008) responded to the surveys.
Ben Sowter, head of the QS Intelligence Unit, which compiled the rankings, said: "The rise of University College London and Imperial College in recent years shows that concerted research efforts can result in improved performance in the increasingly competitive field of global higher education."
Dr Wendy Piatt, director general of the Russell Group of Universities, said: "The broad message of these tables is clear - the leading UK research universities are held in high esteem internationally.
"But countries like China and Korea, which are investing massively in their best institutions, are snapping at our heels.
"The precise accuracy of league tables like this can be debated, but there is no mistaking the alarm bell warning that our success is at risk if we as a nation don't take action to fight off such fierce competition."
A spokesman for Oxford University said the institution's new position was "surprising" and highlighted its strong performance in other league tables and in the Research Assessment Exercise (RAE), which rank universities according to the quality of their research.
Professor Malcolm Grant, president and provost at University College London, said: "We are pleased by UCL's spectacular progression up the tables in recent years, because it does reflect the truly outstanding quality of UCL's community of academics and of our students from around the world."