Gudai-Darri, approved in late 2018, represents Rio's first greenfields Pilbara iron ore development in over a decade.
The new mine sits about 35km northwest of Rio's Yandicoogina mine, and about 110km from Newman.
The first autonomous trains loaded with ore from Gudai-Darri's process plant have travelled the new 166km rail line that connects to Rio's existing rail and port infrastructure.
First production was initially expected in late 2021 but was delayed slightly due to the impacts of COVID-19 on travel, labour and supply chains.
Production from the mine will continue to ramp up through the remainder of the year and is expected to reach full capacity of 43 million tonnes per annum during 2023.
Rio maintained 2022 group iron ore shipment guidance of 320-335Mt, weighted towards the second half of the year.
When approved, Gudai-Darri's capital costs were forecast at $2.6 billion.
However, the company previously disclosed potential capital increases of 15% due to ongoing COVID-19 restrictions, including labour access and supply chain quality issues.
Group capital expenditure guidance for 2022 is unchanged at around $8 billion.
"The commissioning of Gudai-Darri represents the successful delivery of our first greenfield mine in over a decade, helping to support increased output of Pilbara Blend, our flagship product," Rio Iron Ore chief executive Simon Trott said.
"It sets a new standard for Rio Tinto mine developments through its deployment of technology and innovation to enhance productivity and improve safety.
"I'd like to acknowledge the support of the traditional owners, the Banjima People, on whose country Gudai-Darri is situated. We have worked closely with the Banjima People to progress this project and we look forward to continuing to actively partner with them into the future."
Rio chief technical officer Mark Davies said Gudai-Darri was the company's most technologically advanced mine.
"This suite of autonomous assets complements the planned deployment of other leading-edge technologies including a robotic ore sampling laboratory, field mobility devices for all personnel and a digital asset of the fixed plant, which, together with data analytics, will make Gudai Darri safer and more productive," he said.
Gudai-Darri will be powered by a 34 megawatt solar farm that is expected to supply about a third of the mine's average electricity demand once construction is complete in August.
Together with a new lithium-ion battery energy storage system in Tom Price, the solar plant is estimated to reduce annual carbon dioxide emissions by about 90,000 tonnes compared to conventional gas-powered generation, equivalent to taking about 28,000 cars off the road.
