New York City Transit buses, marked on the buses MTA New York City Bus, is a bus service that operates in all five boroughs of New York City, employing over 4300 buses on 219 routes within the five boroughs of New York City in the United States. The bus system is meant to complement the MTA's rail lines - the New York City Subway, Staten Island Railway, Long Island Rail Road, and Metro-North Railroad.

New York City Transit bus routes are spread out citywide. Some lines, such as the Q5 and Q85 cross the Nassau County border to go the Green Acres Mall in Valley Stream. The Q2 and Q110 leave Queens as they run along Hempstead Turnpike and onto the Cross Island Parkway, and Belmont Racetrack in Elmont, where they re-enter the city. The Q46 runs along Lakeville Road in Lake Success, Nassau County upon entering Long Island Jewish Medical Center. The Bx16 bus runs in to Westchester County for two blocks in Mount Vernon. The Bx7 and the Bx10 both make their last stops at the Bronx-Westchester border.

The S89 is the only route to have a stop outside state borders, terminating at the 34th Street Hudson-Bergen Light Rail station in Bayonne, New Jersey. Some Staten Island express routes run via New Jersey, but do not stop in the state. Buses are labeled with a number and a prefix identifying the primary borough (B for Brooklyn, Bx for the Bronx, M for Manhattan, Q for Queens, and S for Staten Island). Express buses use the letter X rather than a borough label. Lettered suffixes can be used to designate branches or variants. MTA Bus Company routes also follow this scheme, and MTA Long Island Bus uses N for Nassau County. W or BL and S are commonly used by the non-MTA Bee-Line Bus System (Westchester County) and Suffolk Transit (Suffolk County). Between 10:00 PM (22:00) and 5:00 AM (05:00) "Request-a-Stop" service is available. The bus operator may discharge passengers at a location along the route that is not a bus stop, as long as it is considered safe. If the location is not "safe", the bus operator will discharge passengers at the nearest safe location. The same policy also applies to MTA Bus and Long Island Bus service (with restrictions for Long Island Bus).

Local and limited-stop buses provide service within a borough, or in some cases across two. While local buses make all stops along a route, limited-stop buses only make stops at busy transfer points, points of interest, and heavily used roadways. Limited stop service was first attempted with the M4 bus during rush hours in 1973, then expanded to other routes from there. The usual setup is that limited stop service runs the full route, while local services run only in the limited stop area, and the limited stop buses run local at the tail ends of the route not served by locals, similar to the operation of some subway lines and the Staten Island Railway.

The following New York City Bus routes run limited stop service:

• Bronx: Bx1, Bx36, Bx41 and Bx55
• Brooklyn: B6, B35, B38, B41, B44, B46, B49 and B82
• Manhattan: M1, M2, M4, M5, M98 and M101
• Queens: Q4, Q5, Q17, Q27, Q36, Q43, Q44, Q46, Q50, Q53, Q58, Q83 and Q85
• Staten Island: S81, S84, S86, S89, S90, S91, S92, S93, S94, S96 and S98

Limited-Stop buses flash LIMITED on the destination sign and usually have an orange Limited sign in the windshield.

Select Bus Service (SBS), the brand name for MTA bus rapid transit service, is a variant of Limited-Stop bus service that requires fare payment to be made before boarding the bus, at fare payment machines in shelters at designated "stations" (such a shelter is shown to the left). On these buses, the operator is only able to dispense transfers, and then only for customers who had to pay their fare in coins. Receipts given for payment of fare are "proof-of-payment" that must be shown to fare enforcement upon request. In the event of the fare machine failing to issue a receipt, the bus operator must be notified of the problem. The implementation of this new service is paired with new lane markings and traffic signs that reserve a lane for buses only between 7AM and 7PM.

SBS began on the Bx12 Fordham Road/Pelham Parkway line in the Bronx on June 28, 2008. The M15 First/Second Avenues line saw SBS implementation on October 10, 2010, and the B44 Nostrand Avenue lines will see implementation in 2011. Variants are also being implemented on 34th Street, 5 Avenue, and Madison Avenue in Manhattan.

Buses used in this service are identifiable with blue lights on the sides of the destination sign and "stations" be similar to those pictured to the right, and also have a +selectbusservice wrap identifying them as such buses. Locations of stops (and in some cases, the local bus stops) were shifted or eliminated where possible to prevent mixing of local bus customers. SBS is offered in conjunction with the New York City and New York State Department of Transportation

Express buses usually operate between Midtown Manhattan or Lower Manhattan and the other boroughs. While most express routes operate only during peak weekday hours, some routes (including the X1, X10, and X17 and various MTA Bus lines) run on a daily basis (the X27 and X28 run all day on weekdays), from about 5:00 AM to 1:00 AM. MCI D series over-the-road coaches are used for express service.

In addition to a 100% accessible bus fleet, New York City Transit also provides paratransit services under the Americans with Disabilities Act (ADA) of 1990 under the Access-A-Ride brand, for customers who cannot use regular bus or subway service servicing all five boroughs of New York City at all times. This system was acquired from the NYC Department of Transportation in 1993.

Within New York City, the color of the route on a bus stop sign indicates the type of service run. Routes are branded on bus stop signs, which are normally located every 2-3 blocks apart in most cases, as follows: