Victory condition

You are declared the Winner when any of the following conditions are met:

Normal win conditions

These are the typical ways to win in the game's mechanics.

Your opponent's Life Points drop to 0.
Your opponent runs out of cards when he/she is required to draw a card, either as part of his/her Draw Phase, or as part of a card effect, such as Morphing Jar. Note the difference between "draw" and "pick up"; you do not win if your opponent is required to pick up a card from his/her deck and he/she can't comply.
Although in most major tournament and non-tournament duels, they are timed for certain reason(s). So the player with the most Life Points by the end of the time limit wins the duel.

These cards allow you to win the duel through its effect.

Exodia the Forbidden One: If you hold "Exodia the Forbidden One" along with "Left Arm of the Forbidden One", "Right Arm of the Forbidden One", "Left Leg of the Forbidden One", and "Right Leg of the Forbidden One" in your hand at once you win the duel by Exodia the Forbidden One's effect.

Exodius the Ultimate Forbidden Lord: If "Exodia the Forbidden One", "Left Arm of the Forbidden One", "Right Arm of the Forbidden One", "Left Leg of the Forbidden One", and "Right Leg of the Forbidden One" are sent to the graveyard by Exodius the Ultimate Forbidden Lord's effect you win the duel. Exodius the Ultimate Forbidden Lord sends monsters from your hand or Deck to the graveyard every time it attacks.

Destiny Board: If "Destiny Board", "Spirit Message "I"", "Spirit Message "N"", "Spirit Message "A"", and "Spirit Message "L"" are all on your side of the field Destiny Board's effects will let you win the duel provided that you placed them on the field in the above order. Destiny Board's effect allows you to place one of the "Spirit Message" cards from your hand or deck onto the field during each of your opponent's turns.

Final Countdown: Once Final Countdown is activated, you win in twenty turns. It only works if the player that played this card doesn't get beaten within 20 turns of the card's activation.

Last Turn: When you activate Last Turn you choose one monster on your side of the field, all other cards on the field are and in player's hands are sent to the graveyard. Your opponent Special Summons a monster from his/her Deck. A special Battle Phase occurs in which the two monsters battle (battle damage is ignored). The player whose monster remains alone on the field at the End Phase of this turn wins the Duel. This strategy is currently forbidden in the advanced format.

Vennominaga the Deity of Poisonous Snakes: If Vennominaga the Deity of Poisonous Snakes on your side of the field has three Hyper-Venom Counters on it you win the duel. Vennominaga the Deity of Poisonous Snakes gains a Hyper Venom Counter every time it inflicts Battle Damage to your opponent's Life Points.

Match Winners: If a Match Winner attacks your opponent directly and makes his/her Life Points 0 by the Battle Damage it inflicted, you win the entire Match.