The US Federal Reserve has raised interest rates by 0.25 percentage points - its first increase since 2006.
The move takes the range of rates banks offer to lend to each other overnight - the Federal Funds rate - to between 0.25% and 0.5%.
The move is likely to cause ripples around the world, and could increase pressure on the UK to raise rates.
It could also mean higher borrowing costs for developing economies, many of which are already seeing slow growth.
Rates in the US have been at near-zero since 2008.