Harris emerged as the Democratic candidate a little more than a month ago when allies of President Joe Biden, 81, forced him to quit the race. If successful, she stands to make history as the first woman elected US president.
Harris, 59, plans to talk about her life as the daughter of a Jamaican father and Indian mother and lay out her plans to tackle rising costs and advance personal freedoms, including abortion rights, aides said.
Her presidential ambitions were apparent for years, but they had been undermined by her own shaky 2020 campaign and bumps along the way of her nearly four years as vice-president.
In a speech that will cap the four-day event in a Chicago arena, she will also deliver a robust denunciation of former president Trump, the aides said.
“There is a guy who wants to divide us, and she will make the case that we simply cannot let that happen, that this is America and everybody can rise together,” Cedric Richmond, campaign co-chair and longtime adviser to Harris, told Reuters.
Speculation has swirled in convention hallways around whether megastar Beyonce will appear. Country band The Chicks was due to sing the national anthem, and Pink will perform.
The speakers list includes members of the Central Park Five, Black men who were wrongly convicted of rape as teenagers and incarcerated for years. Victims of gun violence, including former US representative Gabby Giffords, will also appear.
Former US representative Adam Kinzinger, one of the 10 House Republicans who voted to impeach then-president Trump, is one of several Republicans to speak at the convention for Harris and against Trump.
Over the last three days, Democrats have sought to define themselves as the voice of American values from small towns to overseas.
Her forceful stump speeches have been met by a surge in enthusiasm from voters ahead of the Nov 5 election. Harris has raised a record-breaking US$500 million in a month and has narrowed the gap or taken the lead against Trump in many opinion polls of battleground states that will decide the election.
Unresolved Gaza issues
Outside the convention centre, about 200 Palestinian supporters gathered to protest US support for Israel as it wages war in Gaza. The issue is one of the most divisive among Democrats and got little attention at the convention, which could hurt them at the polls.
Harris has yet to articulate much of her vision for the country, and Republicans say Democrats have spent more time attacking Trump than elaborating on how they would govern.
Harris has spent weeks on the speech, making changes to drafts from lead speechwriter Adam Frankel, including during campaign trips on Air Force Two.
Aides say she will discuss her plans to cut taxes for most Americans, boost the housing supply and ban what she calls “price gouging” by grocers. Her campaign has also proposed raising the corporate tax rate from 21% to 28%.
The speech will include elements of foreign policy along with stories of women affected by abortion bans and other curbs on reproductive rights, aides and advisers said.
Trump, campaigning this week in a handful of battleground states, accused Harris at an Arizona stop along the US-Mexico border of not doing enough to prevent illegal immigration.