Is There an Adapter to Play Game Boy Games on Nintendo DS?

No official adapter exists.

Why?

• Different Cartridge Formats: Game Boy (GB/GBC) and Game Boy Advance (GBA) cartridges are physically and electrically incompatible with the DS slot.
• Hardware Limitation: The DS/DS Lite includes a GBA slot for backward compatibility, but cannot run original GB/GBC software natively (lacks the Sharp LR35902 CPU / Z80 compatibility mode).

Unofficial Options

• Flash Carts: EZ Flash IV, M3 Real, EverDrive GB (for GBA slot) emulate GB/GBC/GBA via software. Require microSD card.
• DSiWare Virtual Console: Previously sold select GB/GBC games (service discontinued, no longer purchasable).

Caveats

• May be considered piracy if you don't own original cartridges.
• Compatibility varies; glitches, save issues possible.

Best Legal Route

• Original Game Boy / Game Boy Color / GBA hardware.
• Nintendo Switch Online (includes select Game Boy & Game Boy Color titles).