The M Queens Boulevard/Sixth Avenue Local[3] is a rapid transit service in the B Division of the New York City Subway.

Its route emblem, or "bullet", is colored orange since it is a part of the IND Sixth Avenue Line in Manhattan.

Though the full route length between 71st Avenue and Metropolitan Avenue is about 18.2 miles (29.3 km), the stations are geographically located 2.47 miles (3.98 km) apart, marking this as the shortest geographic distance between termini for any New York City Subway service that is not a shuttle service.

[5] An MJ service ran the entire BMT Myrtle Avenue Line until 1969, when the section west of Broadway in Brooklyn was demolished.

[10] By 1920, trains later began running express in the morning rush hour and on Saturday afternoon in the peak direction.

[13] On February 10, 1958, the four rush hour Brighton-Nassau special trains began stopping at Neck Road and Avenue U.

[13] In 1961, with the arrival of new R27s which featured rollsigns with new lettered designations for the BMT's numbered services, the 10 was renamed the M.[16][17] Since these cars were not assigned to the route,[18] it remained signed as 10.

Late morning and early afternoon D trains would from then on run express from Brighton Beach to Kings Highway.

Service began terminating at Ninth Avenue during middays, and at Bay Parkway during rush hours.

The elimination of midday M service to Brooklyn was part of a larger plan to reduce spending in order to avert a fare increase, which Governor George Pataki and Mayor Rudy Giuliani had pressured the MTA to avoid.

[43] Truncation of midday M service was proposed as early as January 1991 for an October implementation of that year, subject to approval from the MTA board.

[44] From May 1 to September 1, 1999, the Williamsburg Bridge subway tracks were closed for reconstruction, splitting M service in two sections.

Fares on the B39 bus crossing the Williamsburg Bridge were eliminated and free subway-bus transfers were given at Marcy Avenue and at Delancey Street.

[46] The project cost $130 million, including replacing the tracks' support structure, signal systems and other equipment.

When full Manhattan Bridge service was restored, midday M service was cut back to Chambers Street and replaced in south Brooklyn by the D.[48][49][50] Neighborhood leaders in Chinatown were angered by the decision to terminate midday at Ninth Avenue, instead of running it to Bay Parkway.

A spokesman for New York City Transit stated that it was easier to terminate trains at Ninth Avenue and that a signal upgrade project was going on further down the line.

[53] Then it was extended full-time over the BMT Sea Beach Line to Stillwell Avenue, replacing the N, until October 28.

[60][61] On November 20, 2008, in light of severe budget woes, the MTA announced a slew of potential service cuts; among them was the potential elimination of rush-hour M service which had extended beyond Chambers Street on the Nassau Street Line in Lower Manhattan to Bay Parkway on the West End Line in Brooklyn.

[62] In May 2009, after the New York State Legislature passed legislation to offer financial support to the MTA, the service cut was taken off the table.

[63] However, in late 2009, the MTA once again discovered that it was confronting another financial crisis; most of the same service cuts threatened just months earlier were revisited.

[76][77][78] When the Fresh Pond Bridge project was completed on September 2, 2017, two six-car shuttle trains began operating between Metropolitan and Wyckoff Avenues at all times, running separately from each other on each of the two tracks; two additional six-car trains were stored in the Fresh Pond Yard in order to swap consists in and out of service.

The M had to run to 96th Street because of capacity reductions on the Queens Boulevard Line due to ongoing weekend construction.

[20] The western half of the Myrtle Avenue Line closed on October 4, 1969, ending MJ service, which was replaced with a free transfer to the B54 bus.

[95] Several days before the scheduled closing date, some supports for the elevated structure were hit by a truck, temporarily suspending service.

Timber reinforcement was applied to damaged pillars, allowing service to resume until the scheduled closing date.