The nuclear deal, if implemented, will showcase Russia's ability to export not only energy, but also high-tech products to new Asian markets, at a time when the West is increasing pressure on it through sanctions.
Putin said Russia would put $400 million into a joint investment fund of $500 million to finance projects in Uzbekistan.
Mirziyoyev also said Tashkent was interested in buying more oil and gas from Russia, a reversal of decades-long practice where Moscow imported hydrocarbons from Central Asia.
The Uzbek president described Putin's visit as "historic".
"It heralds the beginning of a new age in the comprehensive strategic partnership and alliance relations between our countries," he said.
Putin also called Tashkent Moscow's "strategic partner and reliable ally".
According to documents published by the Kremlin, Russian state nuclear firm Rosatom will build up to six nuclear reactors with a capacity of 55 megawatts each in Uzbekistan, a much smaller-scale project than the 2.4 gigawatts one agreed in 2018 which remains to be finalised.
There are no nuclear power plants in any of the five ex-Soviet Central Asian republics, although Uzbekistan and its neighbour Kazakhstan, both uranium producers, have long said their growing economies needed them.
The Kazakh project, however, can only move ahead after a national referendum which has not yet been scheduled.
"Nearly all the leading countries of the world ensure their energy security and sustainable development with the help of nuclear energy," Mirziyoyev said.
ENERGY SUPPLIES
Taking advantage of Russia's campaign to redirect its gas exports to Asia amid a rift with the West over Ukraine, Uzbekistan last October started importing Russian natural gas via the same pipeline which had previously pumped it in the reverse direction.
Although its own gas production remains substantial at about 50 billion cubic metres a year, Uzbekistan struggles to fully meet domestic demand, and Russian supplies have allowed it to avert an energy crisis.
"(Gas) exports are running well ahead of schedule and we are ready to increase their volume if needed," Putin said.
According to Mirziyoyev, Tashkent is also keen to increase imports of Russian oil.
The two leaders also said their governments were working on large projects in mining, metals, and chemicals.
Uzbekistan, whose economy depends heavily on remittances from migrant labourers working in Russia, has maintained close ties with Moscow after it invaded Ukraine in 2022.
However, Mirziyoyev and other leaders in the region have never spoken in support of what the Kremlin calls its special military operation in Ukraine, and all countries in the region are also working with the West on projects such as cargo shipping routes designed to bypass Russia.
