M99 or M-99 may refer to:

Places

M-99 (Michigan highway) M-99 is a north–south Michigan State Trunkline Highway System, state trunkline highway in the Lower Peninsula of Michigan, Lower Peninsula of the US state of Michigan. It runs from the Ohio state border, where it connects to Ohio State Route 1 ...

, a state highway in south central Michigan *

Messier 99 Messier 99 or M99, also known as NGC 4254, is a grand design spiral galaxy in the northern constellation Coma Berenices approximately from the Milky Way. It was discovered by Pierre Méchain on 17 March 1781. The discovery was then reported to ...

, an unbarred spiral galaxy approximately 60 million light-years away in the constellation Coma Berenices *

M99 road (Johannesburg) The M99 is a short Metropolitan Routes in Johannesburg, metropolitan route in Johannesburg, South Africa. For its entire route, it parallels the R24 (South Africa), R24 Highway (Albertina Sisulu Freeway) in the City of Ekurhuleni Metropolitan M ...

, Metropolitan route in the City of Johannesburg, South Africa

Rifles

* Barrett M99, a sniper rifle *

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

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 r ...

(a.k.a. Immobilon or M99), a veterinary tranquilizer {{Letter-NumberCombDisambig