Tehran and Moscow both have huge oil and gas reserves but are constrained by sanctions that limit their ability to export their output.
"Upon his arrival in Tehran, Lavrov met with President (Ebrahim) Raisi," state television's website Iribnews reported, without elaborating.
During his two-day visit, Russia's top diplomat is expected to discuss with Iranian officials the 2015 "nuclear deal, the situations in Ukraine, Syria and Afghanistan, and boosting commercial and energy cooperation", Iribnews added.
Lavrov will meet with his Iranian counterpart Hossein Amir-Abdollahian on Thursday, official news agency IRNA said.
Russia was slapped with sanctions following the Russo-Ukrainian war, while Iran's economy has been reeling under biting sanctions reimposed by the US in 2018, following Washington's withdrawal from a nuclear accord between Tehran and major powers.
Russia played a key role in that deal, taking charge of Iran's excess enriched uranium stocks beyond those permitted under the agreement.
It has been party to stumbling talks between Iran and the powers on reviving the 2015 deal with renewed US participation.
The negotiations have been stalled since March amid sharp differences between Tehran and Washington on the US sanctions that would be lifted in exchange for Iran's return to full compliance with the agreed limits to its nuclear activities.
Iran's Raisi visited Moscow in January and said he had presented his counterpart Vladimir Putin with draft documents on strategic cooperation that would cement collaboration for the next two decades.
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