The flag for British Indian Ocean Territory, which may show as the letters IO on some platforms. The same flag is used for Diego Garcia.
The Flag: British Indian Ocean Territory emoji is a flag sequence combining ? Regional Indicator Symbol Letter I and ? Regional Indicator Symbol Letter O. These display as a single emoji on supported platforms.
Flag: British Indian Ocean Territory was added to Emoji 1.0 in 2015.
U+1F1EE
U+1F1F4
?? Regional indicator symbol letter i
?? Regional indicator symbol letter o