He is expected to use meetings with the country’s leaders to press for the release of more political prisoners.
His visit is the latest in a series by top diplomats from around the world, amid steps towards reform by the new government in Burma.
Burma held its first elections in 20 years in 2010, replacing military rule with a nominally civilian government.
Since then the new administration has freed pro-democracy leader Aung San Suu Kyi and begun a process of dialogue.
Last month she formally registered her National League for Democracy as a political party, after boycotting the 2010 polls because of electoral laws that prevented her taking part.
In December US Secretary of State Hillary Clinton visited Burma, in what was seen as an endorsement of the reform process – although Western observers say much more is needed.
Speaking ahead of his arrival in the capital, Nay Pyi Taw, William Hague welcomed the “encouraging” steps taken by the government.
“I am visiting the country to encourage the Burmese government to continue on its path of reform, and to gauge what more Britain can do to support this process,” he said.
Mr Hague is the first British foreign secretary to visit Burma since 1955.
In Nay Pyi Taw he will hold talks with President Thein Sein, a former top general who stepped down to contest the polls as a civilian.
He will then travel to Rangoon, Burma’s commercial capital, to meet Aung San Suu Kyi, representatives of some of Burma’s ethnic minority groups and dissidents.
Ms Suu Kyi’s party plans to contest by-elections in April that could see her elected to parliament. Her party secured a landslide victory in polls in 1990 but was never allowed to take power.
The new government has released some political prisoners in recent months but between 600 and 1,000 journalists, dissidents and monks who led anti-government protests in 2007 are thought to remain behind bars.
Mr Hague said he wanted to see more progress on reform.
“Further steps are needed that will have a lasting impact on human rights and political freedom in Burma,” he said.
“In particular, we hope to see the release of all remaining political prisoners, free and fair by-elections, humanitarian access to people in conflict areas, and credible steps towards national reconciliation.”
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