Police and emergency services were searching for the young girl yesterday night with activity around North Bridge.
A body was found in the water off Paris Gates last night (Monday).
A spokesperson for West Yorkshire police said: "Following the discovery of a body in the river at Paris Gates in Halifax yesterday (January 22) police can confirm that 11-year-old Ursula Keogh was found deceased.
"Police are working to establish the full circumstances and will prepare a file for the coroner.
"Her family are being supported by specialist officers and have requested for privacy at this extremely difficult time."
Lightcliffe Academy confirmed on their Twitter account that Ursula was a pupil at the school. The statement said: "Following the tragic death last night of our student Ursula Keogh, the academy is open today as we look to support students and the whole academy community with this heartbreaking loss.
"Our thoughts and prayers are with Ursula’s family and friends and at this very difficult time."
West Yorkshire Police are continuing to look into the cause of death - but at this point the police don't believe there are any suspicious circumstances.
Readers have also paid tributes and offered their condolences to family and friends on the Halifax Courier Facebook page.
Angela Bottomley said: "Heartbreaking, totally heartbreaking. Rest in peace."
Marilyn Ogden: "My thoughts and prayers are with her family so sad."
Julie Ackroyd: "Absolutely heartbreaking. Can't imagine what this poor baby's family are going through."
Margaret Berry: "So so sad our thoughts go out to the family & friends at this sad time."
Sharon Wood said: "So heartbreaking gone at such a young age thoughts and prayers to her family and friends at this very sad time."