A decade-long UN arms embargo on Iran that barred it from purchasing foreign weapons such as tanks and fighter jets has expired as planned under its nuclear deal with world powers, despite objections from the United States.
While insisting it plans no "buying spree", Iran in theory can purchase weapons to upgrade military armaments dating to before its 1979 Islamic Revolution and sell its own locally produced gear abroad.
In practice, however, Iran's economy remains crippled by broad-reaching US sanctions and other nations may avoid arms deals with Tehran for fear of American financial retaliation.
The Islamic Republic heralded the end of the arms embargo on Sunday as "a momentous day for the international community ... in defiance of the US regime's effort".
The Trump administration, meanwhile, has insisted it has re-invoked all UN sanctions on Iran via a clause in the nuclear deal it withdrew from in 2018, a claim ignored by the rest of the world.
The United Nations banned Iran from buying major foreign weapon systems in 2010 amid tensions over its nuclear program. An earlier embargo targeted Iranian arms exports.
Iran long has been outmatched by US-backed Gulf nations such as Saudi Arabia and the United Arab Emirates, which have purchased billions of dollars of advanced American weaponry.
In response, Tehran turned towards developing locally made ballistic missiles.
Sunday also marked the end of UN travel bans on a number of Iranian military and paramilitary Revolutionary Guard members.
Tensions between Iran and the US reached fever pitch at the start of the year, when an American drone killed top Iranian general Qasem Soleimani in Baghdad.
Tehran retaliated with a ballistic missile attack on US forces in Iraq that injured dozens.
Australian Associated Press