FRANKFURT, Germany — Greece officially completes its bailout program on Monday, after eight years of cutbacks enforced in return for massive loans and following an economic collapse on the scale of the Great Depression.

The exit is a welcome milestone. But it offers little assurance that the 19-country euro currency union has left behind its problems with debt. The huge debt pile in Greece and an even bigger one in Italy will remain a lurking financial threat to Europe that could take a generation to defuse.

Europe’s debt problems have repeatedly raised fears over the past decade of a breakup in the euro, a worst-case scenario that would cause severe economic damage in the region and shake world financial markets and trade.

In Greece, successive governments had borrowed heavily for three decades to fund generous spending on pensions and jobs given to political supporters, while tolerating widespread tax evasion and covering up budget shortfalls. All that blew up in October 2009, when Greece admitted its budget deficit was much bigger than previously reported. Shocked investors no longer would risk loaning money at affordable rates, forcing the government to turn to rescue loans from the other eurozone countries.

The loans came with tough conditions: closing deficits, which led to aggressive tax increases and spending cuts; and a raft of reforms aimed at improving tax collection and the business climate in general.

All told, Greece now owes total debt of $366 billion, or over 180 percent of annual economic output.