Matt Mii refers to a CPU opponent from Wii Sports, Wii Sports Resort and Wii Party video games for the Wii video game console. In memes, the character is often referred to as the strongest opponent in Wii Sports, with his abilities humorously exaggerated.
On November 19th, 2006, Wii Sports sports video game was released by Nintendo for Wii video game console. The game had 60 pre-made CPU opponents, or CPU Miis, which human players could compete against in Tennis, Baseball and Boxing mini-games (more disciplines were included in the later games of the series).
Among CPU opponents, in Wii Sports games Matt Mii (shown below) is the only CPU to have championship status in more than one discipline, being the hardest NPC to beat both in Boxing and Swordplay. While his performance in different disciplines varies between the installments, in each Wii Sports game Matt excels in at least at one sport, and is a Master Mii in Wii Party.
In 2018, memes in which Matt Mii appeared as a tough, near-unbeatable opponent, gained popularity on Reddit. On May 20th, 2018, Redditor AydanOfHouseCock posted the first known meme featuring the character to /r/dankmemes subreddit. The post gained over 7,200 upvotes in six months. On July 10, 2018, Redditor PepperSprayP made another post which received over 21,100 upvotes in six months.