Lead researcher Professor John Howl, of Wolverhampton University in England, said the new compound, made in the lab, had shown immediate results.
"The results are startling - and almost instant. When you take healthy sperm and add our compound, within a few minutes the sperm basically cannot move," he said.
Working with scientists from Portugal, the team made a compound called a cell-penetrating peptide.
Peptides are short chains of amino acids which influence how human cells work. They occur naturally but can also be created synthetically.
The breakthrough came after scientists in Wolverhampton demonstrated that particular peptides could penetrate sperm cells. Then fertility experts at Aveiro University in Portugal, who had identified the protein that drives sperm to swim, created a bespoke compound that turned the protein off.
The approach was tested in the lab on bovine and human sperm, with live animal tests due to start within three years.