M99 or M-99 may refer to:
Places
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M-99 (Michigan highway)
M-99 is a north–south state trunkline highway in the Lower Peninsula of the US state of Michigan. It runs from the Ohio state border, where it connects to State Route 15 (SR 15), north to Lansing, where it terminates at a junctio ...
, a state highway in south central Michigan
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Messier 99, an unbarred spiral galaxy approximately 60 million light-years away in the constellation Coma Berenices
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M99 road (Johannesburg), Metropolitan route in the City of Johannesburg, South Africa
Rifles
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Barrett M99, a sniper rifle
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Zijiang M99
The Zijiang M99 is a semi-automatic anti-materiel rifle first introduced in 2005. It has since seen use by the People's Liberation Army Navy and Marine Corps in anti-piracy operations in the Gulf of Aden, and has been seen in the hands of variou ...
, a Chinese anti-materiel rifle
Tranquilizer
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Etorphine
Etorphine (M99) is a semi-synthetic opioid possessing an analgesic potency approximately 1,000–3,000 times that of morphine. It was first prepared in 1960 from oripavine, which does not generally occur in opium poppy extract but rather the re ...
(a.k.a. Immobilon or M99), a veterinary tranquilizer
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