America’s First Lady Michelle Obama has shown why she’s worth plagiarising.

On the first night of the Democratic convention, she brought the house down, with delegates and social media going wild with praise over her speech.

In backing former First Lady Hillary Clinton, Mrs Obama described America as “the greatest country on earth”, clashing with Republican Donald Trump’s “Make America Great Again” slogan and bringing an arena crowd driven by a fierce fight for the nomination to its feet.

“Don’t let anyone ever tell you that this country isn’t great, that somehow we need to make it great again, because this right now is the greatest country on earth,” she said.

Bill Clinton claps during first lady Michelle Obama’s speech. Photo: Getty

One critic said she managed to disassemble Trump’s entire narrative without ever mentioning his name.

President Obama lauded her performance.

“Incredible speech by an incredible woman. Couldn’t be more proud & our country has been blessed to have her as FLOTUS. I love you, Michelle,” he wrote in a Twitter post, using an acronym for the first lady of the United States.

Incredible speech by an incredible woman. Couldn't be more proud & our country has been blessed to have her as FLOTUS. I love you, Michelle.

— President Obama (@POTUS44) July 26, 2016

His tweet became the most re-tweeted post of the night.

Michelle Obama told the convention: “I wake up every morning in a house that was built by slaves, and I watch my daughters – two beautiful, intelligent, black young women – playing with their dogs on the White House lawn.”

Watch her full speech below:

The speech triggered wild applause among delegates in the Wells Fargo Center, where anger over Senator Bernie Sanders’ loss in the primary elections against Clinton had taken the form of jeers during speeches earlier in the day.

Some Sanders supporters had called out at some points early in Obama’s speech, but were shushed.

Several Twitter users said the speech brought them to tears, while others marvelled at its positive tone in an election year marked by blunt exchanges.

Mrs Obama, a lawyer who has advocated for military families and working women during her seven-and-a-half years as First Lady, has earned a reputation for inspirational speeches.

Last week, during the Republican National Convention, Trump’s wife Melania delivered a speech that appeared to borrow phrases from Mrs Obama’s convention speech in 2008, drawing accusations of plagiarism.