Chipperfield was appointed from a competition field of some 100 candidates.
The choice to use the British architect ends a five-year planning process for an expansion that was originally envisioned in the museum's 2000 strategic plan.
The expansion is expected to encompass around 12,000m 2, which is a 40 per cent increase in space.
'Over the past 125 years, strategic acquisitions by the museum and magnificent gifts from local benefactors have created a collection that places the museum among the top ten comprehensive art museums in the US,' said Saint Louis Art Museum Director Brent R. Benjamin.
But he went on to warn: 'With limited gallery space, however, major works by such artists as Matisse and Picasso are confined to storage and entire collections can only be viewed on a rotating basis.'