Henry Guenther Ademola Dashtu Samuel (search) was born Monday in Los Angeles, the couple announced Wednesday on Klum's German-language Web site.
Seal's full name is Sealhenry Olusegun Olumide Samuel, while Heidi's father and manager is Guenther Klum.
The baby is the couple's first child. The 32-year-old German supermodel has a 16-month-old daughter, Leni, from her previous relationship with Formula One manager Flavio Briatore.
"One of our greatest moments so far was when Leni kissed her little brother many times on the head," the couple said on the Web site.