Students at Copperbelt University (CBU) lit candles and marched around campus to mourn the big fish.
The hashtag Mafishi, as the fish was affectionately known, is trending on Twitter in the southern African state.
For the past two decades CBU students have believed the fish would bring them good luck in exams.
Mafishi, meaning "Big Fish" in the local Bemba language, was thought to be at least 22 years old and had lived in the university's pond for more than 20 years, student leader Lawrence Kasonde said.
His death was still being investigated, added the president of the Copperbelt University Student's Union.
"It is yet to be buried, we are planning on embalming it," Mr Kasonde told the BBC.
Some students used to pay homage to the fish before exams, believing it brought them good luck while others saw it as a stress-reliever, says BBC Zambia reporter Kennedy Gondwe.