“Stop the violence and looting,” she also said as protests continued over a police shooting in Wisconsin.
Mrs Trump urged Americans to stop making assumptions based on race and reflected candidly on US history
What did Melania Trump say?
The normally limelight-shunning US first lady delivered Tuesday evening’s keynote address before a small audience, including her husband, in the Rose Garden of the White House.
“Like all of you, I have reflected on the racial unrest in our country,” she said.
“It is a harsh reality that we are not proud of parts of our history. I encourage you to focus on the future while still learning from the past.”
She added: “I urge people to come together in a civil manner so we can work and live up to our standard American ideals.
“I also ask people to stop the violence and looting being done in the name of justice, and never make assumptions based on the colour of a person’s skin.”
Tuesday’s convention schedule began with a prayer for Jacob Blake, the 29-year-old black man shot multiple times in the back by police in Wisconsin on Sunday.
Mr Trump tweeted a call for the Midwestern state’s governor to bring in the National Guard as unrest continued following the shooting.
The president has often been accused by opponents of stoking racial tension, though black speakers at the opening night of the Republican convention emphatically denied he was racist.
In her speech, Mrs Trump also expressed compassion for Americans worried about the coronavirus outbreak, which has killed more than 178,000 Americans.
“I know many people are anxious,” she said. “Some feel helpless. I want you to know you’re not alone.”