Ms Pelosi became Speaker of the House of Representatives in January this year. Before that she was House minority leader for the Democrats, before they took a majority last November. Ms Ocasio-Cortez, who represents New York’s 14th congressional district, reportedly became the youngest women to ever preside over the House on Friday.
The 26-year old took over for a period of about an hour, as part of a routine operation where the role rotates between lawmakers.
On her Twitter account Ms Ocasio-Cortez commented: “Today I presided over the House floor for the first time.
“Every day here is a sacred privilege and responsibility entrusted to me by my community.
“I never forget that, and moments like these drive it home.
“This House belongs to all of us.”
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Ms Pelosi previously served as Speaker from 2007-2011.
When the formidable Democrat was re-elected after the 2018 mid-term elections she became the first former Speaker to return to the post since 1955.
Ms Pelosi shot to prominence as House Minority Whip from 2002-3, and then as an outspoken critic of the Iraq War.
The prominent Democrat is an unabashed admirer of Ms Ocasio-Cortez.
Last month she described her as “a wonderful member of Congress, as I think all of our colleagues will attest”.
After presiding over the House Ms Ocasio-Cortez spoke of her delight to journalists.
She commented: “That was my first time presiding. And it’s exciting.
“It’s certainly a view, I wish we were allowed to take photos.”