How many people total is needed to play D&D (Dungeons and Dragons)?
At minimum, at least two. One person to be Dungeon Master, and the other to be a player. Its better with more players though. I would say the optimum is one Dungeon master, and four players.
2 or 3 would be possible, it's better to have at least 4 though (a DM and 3 player characters)
At a minimum, Dungeons and Dragons can realistically be played with 2 people. Most pre-written, including the starting box, are designed to be played with between 4 and 6 characters. Each character is played by a single person (generally). The system also needs 1 person to be the Dungeon Master, or DM. So generally 5 to 7 people is a good group. Technically you can play with less, but a lot of the fun of D&D comes from the interaction of multiple people controlling multiple characters. You can also play D&D with more people, but the action starts bogging down for people as soon as you have more than 7 characters. (There are systems that aren't D&D that do away with the DM position, or rotate it, to reduce the number of people you need, and there are systems designed to be played with just 1 person. There aren't any systems that are really designed for more than 8 people at once.)
I mean I guess technically you only need 2 although it's more fun with at least another person. 3+ would be my answer.