The "proportionate" strikes were aimed at "Kataib Hezbollah and other Iran-linked groups," Defense Secretary Lloyd Austin said.
He said the precision strikes were a "direct response" to attacks on US and coalition allies in Iraq and Syria.
Several US service members were injured in a missile attack on an airbase in western Iraq last week.
At the time, the US Central Command (CentCom) reported that an Iranian-backed militia had attacked the Al-Assad air base, where US troops are stationed, with ballistic missiles and projectiles.
A group calling itself the Islamic Resistance in Iraq claimed responsibility for the attack.
According to the US-based Washington Institute for Near East Policy, the group emerged in late 2023 and is made up of several Iran-linked armed groups operating in Iraq. It has also claimed other attacks on US forces in recent weeks.
In his statement, Austin praised the US military's "professionalism" in planning and executing the strikes in Iraq as part of an effort to "further defeat and degrade ISIS [the Islamic State group]."
"We do not seek an escalation of conflict in the region. We are fully prepared to take additional measures to protect our people and facilities. We call on these groups and their Iranian sponsors to immediately end these attacks," he said.
In a separate statement, CentCom said the strikes in Iraq were carried out at 00:15 local time (21:15 GMT on January 23) in response to the attack on - among others - Al Asad Air Base in western Iraq on January 20./BGNES
