Sweden cleared the final hurdle to Nato membership on Monday as Hungary's parliament backed the alliance's enlargement.
Hungary became the 31st and final Nato ally to back the Swedish application on what Sweden's Prime Minister Ulf Kristersson called a historic day.
It paves the way for Sweden's formal accession to Nato, which could come in a matter of days.
"Sweden stands ready to shoulder its responsibility for Euro-Atlantic security," Mr Kristersson said. Nato Secretary General Jens Stoltenberg said Sweden's membership "will make us all stronger and safer".
Hungarian MPs voted 188 to six to back Sweden's bid. The nationalist government in Budapest had delayed calling a vote for months even while saying it supported the application in principle.
After Hungary signed a deal on Friday to buy four Swedish-made fighter jets, Prime Minister Viktor Orban relented.
"The Swedish-Hungarian military co-operation and Sweden's accession to Nato will strengthen Hungary's security," he told MPs on Monday.
"Therefore, I ask my fellow members to vote today for the parliamentary resolution on Sweden's accession to Nato."
Sweden and its neighbour Finland turned the page on decades of neutrality to seek Nato's protection after Russia invaded Ukraine in 2022.
Most allies put up no objection but Turkey and Hungary delayed both Nordic countries' applications for months.
Turkey demanded tougher action by both nations against Kurdish militants it regards as terrorists. It eventually backed the Finnish application last year and approved the Swedish one last month.
The reasons for Hungary's foot-dragging were less clear but included complaints about Swedish officials "vilifying" Mr Orban's government and being "keen to bash Hungary", which maintains better relations with Moscow than most Nato countries.
The final step after Hungary's approval is for Sweden to confirm its accession with the US government, which looks after Nato's founding treaty.
Joining the alliance means Sweden is bound by Nato's Article 5 mutual defence clause, in which allies agree to assist each other if one of them is attacked.
Sweden has promised to be a "reliable, loyal and engaged Nato ally".
Its military has already taken part in Nato drills but its full membership will simplify defence planning on the alliance's northern flank. Sweden also brings resources such as cutting-edge submarines tailored to Baltic Sea conditions and a sizeable fleet of domestically produced Gripen fighter jets into the alliance.
Hungary signed a deal with visiting Swedish Prime Minister Ulf Kristersson on Friday to acquire four of those jets, expanding its existing fleet of 14 Jas-39 Gripen fighters.
Nato began with 12 members in 1949 but grew substantially after the end of the Cold War. Finland became its 31st member in April last year.
Western leaders have described Nato's Nordic enlargement as evidence of a huge strategic blunder by the Kremlin, which had sought to avoid such an outcome.
