ATmega328

ATmega328P in 28-pin narrow dual in-line package (DIP-28N)
ATmega328P in 32-pin thin quad flat pack (TQFP-32)
Die of ATmega328P

The ATmega328 is a single-chip microcontroller created by Atmel in the megaAVR family (later Microchip Technology acquired Atmel in 2016). It has a modified Harvard architecture 8-bit RISC processor core.