What is the first 64 bit CPU?

The first 64-bit CPU is generally considered to be the AMD Athlon 64, which was released in September 2003. It was notable for being the first consumer desktop processor to support 64-bit computing, allowing for increased memory addressing and improved performance in 64-bit applications. Other early 64-bit processors include the Itanium from Intel, but the Athlon 64 was the first to gain widespread adoption in the consumer market.