Defar won in 9 minutes, 10.47 seconds, lowering the mark of 9:11.97 set by American Regina Jacobs in 1999.
The crowd at Home Depot Center roared as the 23-year-old runner cruised toward the finish line, leaving her rivals far behind.
Defar grabbed the green, gold and red Ethiopian flag and jogged around the track, stopping to greet well-wishers.
Defar won a gold medal in the 5,000 meters at the 2004 Athens Olympics and Sunday's effort was her fourth world mark.
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