Turnout was 51 per cent, just above the 50 per cent needed to give her an outright first round win and avoid a run-off.
The 53-year-old tough-talking former finance minister ran as an independent candidate, enhancing her popularity in contrast to the main political parties, whose standing were hit by the economic downturn and allegations of corruption.
"I think that together we will be able to emerge from these times of hardships much better ... and much richer"
presidential poll winner
"I think that together we will be able to emerge from these times of hardships much better, much more direct and much richer," she said.
Grybauskaite, a karate black-belt, has said the Baltic state must stabilise its public finances, stimulate exports, absorb EU aid faster and provide tax breaks for small and medium-sized businesses to tackle the economic downturn.
She entered the presidential race in February, after public anger over the economic situation erupted into a riot outside parliament.
The government has slashed public spending, but unemployment is climbing and the economy is forecast to shrink by 15.6 per cent this year.
Lithuania's president appoints the prime minister and cabinet.
The president also has some influence over economic policies, including the right to veto budget laws, but presidential executive powers are limited to implementing foreign and defence policies together with the government.