Born at Rosheim in France, Lehn was educated at Strasbourg where he obtained his PhD in 1963, and at Harvard. After working in Strasbourg from 1966 to 1970, Lehn returned to Harvard as professor of chemistry. In 1979 he took up the chair of chemistry at the Collège de France, Paris.

In 1963 Charles Pedersen had discovered the first of the crown ethers. While Pedersen had worked with two-dimensional rings, Lehn sought to extend his work into three dimensions. If two nitrogen atoms replaced the oxygen atoms of the original crown ether, Lehn found, two crowns could be made to combine into a cage-like structure; a ‘cryptand’ in Lehn's terminology. He found that cryptands were capable of binding metal cations more selectively than the crown ethers. Lehn went on to develop cryptands that would bind selectively with other molecules, including important biologically active molecules as the neurotransmitter, acetylcholine. The molecules found in this way are known as ‘supramolecules’ and their discovery has opened up an important new field known as ‘host–guest chemistry’.

For his work in this new field Lehn shared the 1987 Nobel Prize for chemistry with Pedersen and Donald Cram.