Lebensohl is bridge convention used after an opponent's intervention over 1NT opening bid. It emerged "in wild" in 1960s and was subsequently attributed to Kenneth Lebensold as a misspell, but he denied any contribution. The article about it appeared in 1970. in The Bridge World, by George Boehm.

The convention emerged out of need that the partner of 1NT opening bidder effectively competes over RHO's overcall without committing the partnership to the game. The basic outline after the sequence (1NT by partner-2x by RHO) is:

• 2 in any suit ? natural, non-forcing,
• 3 in any suit except overcalled ? natural, forcing to game,
• cuebid (3 in overcalled suit) ? akin to Stayman convention, inquiring the partner about 4-card major and promising a stopper in the overcalled suit,
• 3NT ? to play, promising a stopper,
• 2NT ? a relay bid forcing the opener to bid 3♣; after that:
  • 3 in suit of lower rank than overcalled ? natural, non-forcing,
  • 3 in suit of higher rank than overcalled ? natural, forcing to game, but denying the stopper,
  • cuebid ? Stayman as above, but denying a stopper in the overcalled suit,
  • 3NT ? to play, denying a stopper.

In summary, the responder must decide whether he has a sign-off or a game-forcing hand (i.e. invitations are not possible). He may freely bid a sign-off on level 2 if there's room, or via 2NT otherwise. With game-forcing hand, he should bid directly on level 3 to promise a stopper, or via 2NT to deny it.

When the responder's long suit is lower-ranked than the overcalled, there's no room to distinguish presence of a stopper.

The above description describes so-called "slow denies" variant, where strong hands must bid 2NT first to deny a stopper. In the "slow shows" variant, direct bid of level 3 denies a stopper and 2NT promises it.