The divide-and-conquer technique is significant in competitive programming because it allows for the efficient solution of large and complex problems by breaking them into smaller, manageable subproblems. This method involves dividing a problem into smaller parts, solving each independently, and combining the results for a complete solution. It is commonly used in algorithms like merge sort, quick sort, and binary search. Divide-and-conquer is highly efficient, often reducing the time complexity from O(n^2) to O(n log n) in sorting, for instance. By mastering this approach, competitive programmers can tackle problems involving sorting, searching, and optimization effectively. Practicing divide-and-conquer problems builds familiarity with recursive thinking and helps in creating efficient solutions, which is crucial in competitive scenarios where time efficiency matters.