The Pentium Pro is a sixth-generation x86 microprocessor developed and manufactured by Intel introduced in November 1, 1995. It introduced the P6 microarchitecture (sometime referred as i686) and was originally intended to replace the original Pentium in a full range of applications. While the Pentium and Pentium MMX had 3.1 and 4.5 million transistors, respectively, the Pentium Pro contained 5.5 million transistors. Later, it was reduced to a more narrow role as a server and high-end desktop processor and was used in supercomputers like ASCI Red. The Pentium Pro was capable of both dual- and quad-processor configurations. It only came in one form factor, the relatively large rectangular Socket 8. The Pentium Pro was succeeded by the Pentium II Xeon in 1998. The Pentium Pro processor powered ASCI Red, the first computer to reach the TeraFlop performance mark.

Belying its name, the Pentium Pro had a completely new microarchitecture, a departure from the Pentium rather than an extension of it. It has a decoupled, 12-stage superpipelined architecture which uses an instruction pool. The Pentium Pro (P6) featured many advanced concepts not found in the Pentium, although it wasn't the first or only x86 processor to implement them (see NexGen Nx586 or Cyrix 6x86). The Pentium Pro pipeline had extra decode stages to dynamically translate IA-32 instructions into buffered micro-operation sequences which could then be analysed, reordered, and renamed in order to detect parallelizable operations that may be issued to more than one execution unit at once. The Pentium Pro thus featured out of order execution, including speculative execution via register renaming. It also had a wider 36-bit address bus (usable by PAE), allowing it to access up to 64GB of memory.