A free app for Android, by Offline Games Dont Need Wifi.
It's one of the most popular free Sudoku puzzles in the Play Store. The rules are very simple: you have to place the numbers from 1 to 9 in a 9×9 grid, but you can't repeat the same number in the same row, column, or quadrant. If you complete the puzzle, you'll get a score and a chance to compare your result with the best players in the world.
If you're a real Sudoku fan, you'll love this game. The gameplay is very simple and intuitive. You can play it even if you have no internet connection, which makes it great for people who don't have access to the Internet or Wi-Fi.