After a yearlong debate, Parliament voted today to end 73 years of prohibition by legalizing beer with an alcoholic content of about 2.25 percent.

A full turnout of the upper house of Iceland's Parliament voted 13 to 8 to permit the sales, ending the last area of prohibition on the island. A dozen beer-lovers flashed victory signs outside Parliament after the results came in, but there was little other public rejoicing.

Beer will not go on sale until March 1989.

A former lawmaker, Jon Magnusson, who supported legalization, said, ''It's important that people realize that beer is as dangerous as other alcohol.''

A leftist member of Parliament, Svavar Gestsson, who opposed legalization, said, ''This is unfortunate and a dreadful experience for me, both as a parent and a parliamentarian.''