PARIS — Having been besieged by the Ottomans, and ruled over the centuries by foreign invaders from the Greeks to the Romans to Napoleon, the tiny Mediterranean island nation of Malta has seen plenty of unwelcome interlopers.

But now, it seems, these foreigners are quite welcome — if they are willing to hand over 1.15 million euros, or $1.55 million, to buy a Maltese passport.

Motivated in part by economic stress, and in part by what some call crass opportunism, the idyllic island 50 miles south of Sicily is selling citizenship for $880,000 in cash and $677,000 in property and investments to applicants 18 or older willing to pay the price.

The Maltese prime minister, Joseph Muscat, has estimated that the program, which is aimed at attracting well-heeled residents from abroad, could bring in $1.35 billion in the next five years, providing welcome financing for schools, health care and jobs.