Hariri praised the recent security gains in Iraq, the government said in a statement. Violence has dropped to a four-year low.
Few senior Lebanese officials have visited Iraq since the U.S.-led invasion in 2003, but regional countries are starting to re-engage with the Shi'ite-led government.
Hariri, son of Lebanon's slain ex-prime minister Rafik al-Hariri, is the Sunni Muslim leader of Lebanon's majority parliamentary coalition.
He also heads a multi-billion dollar business empire, and his visit coincides with an Iraqi push for more foreign investment to help rebuild the country and provide jobs.
Last week Turkish Prime Minister Tayyip Erdogan visited Baghdad, the first Turkish leader to do so since the U.S.-led invasion to topple Saddam Hussein.
Jordan's King Abdullah is also due to visit soon, a trip that would make him the first Arab leader to travel to Iraq since the invasion.
The U.S. military has accused Lebanon's Iranian-backed Shi'ite opposition group Hezbollah of helping train Iraqi militants.
Tags: Hariri, Hezbollah, Iraq, Lebanon, source: Reuters, Ya Libnan
