The Martingale system in tennis betting is a strategy based on doubling your stake after every loss, with the aim of recovering all previous losses and achieving a profit when you eventually win. For instance, if you place a bet of $10 and lose, you would then bet $20 on the next match. If you lose again, you would bet $40 next, and so on. The idea is that eventually winning a bet will compensate for all the losses incurred in prior bets, along with a small profit equal to the initial bet.