A Japanese court has sentenced to death a one-time millionairess dubbed the "Black Widow", who tricked elderly lovers into drinking cyanide and pocketed millions in insurance payouts and inheritance.

Kyoto District Court condemned Chisako Kakehi, 70, to the gallows for the murder of three men - including one husband - and the attempted murder of another, ending a high-profile case that has gripped the country.

Kakehi became notorious after using the poison to dispatch a number of elderly men she was involved with, drawing comparisons with the spider that kills its mate after copulation.

"The accused made the victims drink a cyanide compound with a murderous intention in all the four cases," Judge Ayako Nakagawa told the court, according to public broadcaster NHK.

Nakagawa rejected defence lawyers' arguments that Kakehi was not criminally liable because she was suffering from dementia.