The Pentium II is an x86 architecture microprocessor by Intel, introduced in February 1997. It was based on a modifed version of the P6 core first used for the Pentium Pro, but with improved 16-bit performance and the addition of the MMX instructions which had already been introduced on the Pentium MMX.

The original Klamath Pentium IIs produced an (for that time) incredible amount of heat. This was because of the 0.35Ám fabrication process. They also worked with a 66MHz front side bus, which was a speed that was inadequate for the CPU's design to show its full potential. The Deschutes core Pentium IIs which debued in 1998 were produced on a more suitable 0.25Ám fabrication process, meaning they ran significantly cooler. Support for 100MHz front side bus speeds heralded decent performance improvements.

Unlike previous Intel processors such as the Pentium and Pentium Pro, the Pentium II was packaged in a slot-based form-factor rather than a socket one. Pentium II-based systems also oversaw the introduction of a new generation ram-standard (SDRAM), which replaced EDO RAM.

A low-end version of the Pentium II - essentially a Pentium II with less level 2 cache - was marketed under the name "Celeron". The Pentium II Xeon was a high-end version intended for use on servers.

The Pentium II was eventually superseded by the Pentium III.

see also: List of Intel microprocessors