Pentium III是英特尔的x86（更准确地说是P6）架构之微处理器，于1999年2月26日推出。刚推出的版本与早期的Pentium II非常相似，最值得注意的不同是SSE指令的扩充，以及在每个芯片制造的过程加入了有争议的序号进去。与Pentium II相同，也有低级的Celeron版本和高端的Xeon版本。Pentium III最后被Pentium 4所取代，Pentium III的改进设计就是后来的Pentium M。

The Pentium III (marketed as Intel Pentium III Processor, informally PIII, also stylized as Pentium !!! ) brand refers to Intel's 32-bit x86 desktop and mobile microprocessors based on the sixth-generation P6 microarchitecture introduced on February 26, 1999. The brand's initial processors were very similar to the earlier Pentium II-branded microprocessors. The most notable differences were the addition of the SSE instruction set (to accelerate floating point and parallel calculations), and the introduction of a controversial serial number embedded in the chip during the manufacturing process.