Coordinates: 40°49′54.79″N73°54′19.57″W / 40.8318861°N 73.9054361°W
|Owner||City of New York|
|Length||10.7 mi   (17.2 km)|
|Location||Manhattan and the Bronx in New York City|
|South end||Astor Place / St. Mark's Place in Cooper Square|
| Harlem River Drive in East Harlem |
I-87 in Mott Haven
I-95 in Morrisania/Tremont
|North end||US 1 (Fordham Road) in Fordham|
|West|| Fourth Avenue (between 8th and 14th Streets)|
Irving Place (between 14th and 20th Streets
Lexington Avenue (north of 21st Street)
Third Avenue is a north-south thoroughfare on the East Side of the New York City borough of Manhattan, as well as in the center portion of the Bronx. Its southern end is at Astor Place and St. Mark's Place. It transitions into Cooper Square, and further south, the Bowery, Chatham Square, and Park Row. The Manhattan side ends at East 128th Street. Third Avenue is two-way from Cooper Square to 24th Street, but since July 17, 1960  has carried only northbound (uptown) traffic while in Manhattan; in the Bronx, it is again two-way. However, the Third Avenue Bridge carries vehicular traffic in the opposite direction, allowing only southbound vehicular traffic, rendering the avenue essentially non-continuous to motor vehicles between the boroughs.
The street leaves Manhattan and continues into the Bronx across the Harlem River over the Third Avenue Bridge north of East 129th Street to East Fordham Road at Fordham Center, where it intersects with U.S. 1. It is one of the four streets that form The Hub, a site of both maximum traffic and architectural density, in the South Bronx. 
Like most urban streets, Third Avenue was unpaved until the late 19th century. In May 1861, according to a letter to the editor of The New York Times , the street was the scene of practice marching for the poorly equipped troops in the 7th New York Volunteer Infantry Regiment: "The men were not in uniform, but very poorly dressed, — in many cases with flip-flap shoes. The business-like air with which they marched rapidly through the deep mud of the Third-avenue was the more remarkable." 
Portions of Third Avenue are served by several routes in Manhattan. Buses serving Third Avenue include the Third and Lexington Avenues Line (or Third and Amsterdam Avenues Line). Note that southbound M98, M101, M102, and M103 service operates on Lexington Avenue north of East 24th Street.
Along the Bronx's Third Avenue also run several bus routes:
Third Avenue was the location of the Third Avenue Railroad, a horsecar line established in 1853 that evolved into one of the largest streetcar systems in Manhattan, the Bronx, and Westchester County. Later it was served by the Third Avenue elevated line, which operated from 1878  until 1955 in Manhattan, and 1973 in the Bronx. The Bx55 replaced the Third Avenue Line in the Bronx in 1973. At the time the El was being torn down in Manhattan, there was a movement to rename the whole of Third Avenue in Manhattan "the Bouwerie" (but not the portion in the Bronx), although it had never been part of the Bowery.  Today, the Third Avenue – 149th Street station ( 2 and 5 trains) and Third Avenue – 138th Street station ( 6 and <6> trains) are served by the New York City Subway.
In Manhattan, several crosstown subway routes have entrances on Third Avenue:
The 6 Lexington Avenue Local and <6> Pelham Bay Park Express are two rapid transit services in the A Division of the New York City Subway. Their route emblems, or "bullets", are colored forest green since they use the IRT Lexington Avenue Line in Manhattan.
Park Avenue is a wide New York City boulevard which carries north and southbound traffic in the borough of Manhattan. For most of the road's length in Manhattan, it runs parallel to Madison Avenue to the west and Lexington Avenue to the east. Park Avenue's entire length was formerly called Fourth Avenue; the title still applies to the section between Cooper Square and 14th Street. The avenue is called Union Square East between 14th and 17th Streets, and Park Avenue South between 17th and 32nd Streets.
The Interborough Rapid Transit Company (IRT) was the private operator of the original underground New York City Subway line that opened in 1904, as well as earlier elevated railways and additional rapid transit lines in New York City. The IRT was purchased by the city in June 1940. The former IRT lines are now the A Division or IRT Division of the Subway.
Lexington Avenue, often colloquially abbreviated as "Lex", is an avenue on the East Side of the borough of Manhattan in New York City that carries southbound one-way traffic from East 131st Street to Gramercy Park at East 21st Street. Along its 5.5-mile (8.9-kilometer), 110-block route, Lexington Avenue runs through Harlem, Carnegie Hill, the Upper East Side, Midtown, and Murray Hill to a point of origin that is centered on Gramercy Park. South of Gramercy Park, the axis continues as Irving Place from 20th Street to East 14th Street.
Fordham station, also known as Fordham–East 190th Street station, is a commuter rail stop on the Metro-North Railroad's Harlem and New Haven Lines, serving Fordham Plaza in the Fordham neighborhood of the Bronx, New York City. The platforms are situated just below street level and feature two expanded side platforms that serve eight cars each, on the outer tracks. The station building sits above the tracks on the Fordham Road overpass, and still bears the name New York Central Railroad on its facade. The station is among the busiest rail stations in the Bronx.
The IRT Third Avenue Line, commonly known as the Third Avenue Elevated, Third Avenue El, or Bronx El, was an elevated railway in Manhattan and the Bronx, New York City. Originally operated by the New York Elevated Railway, an independent railway company, it was acquired by the Interborough Rapid Transit Company (IRT) and eventually became part of the New York City Subway system.
Fordham Road is a major thoroughfare in the Bronx, New York City, that runs west-east from the Harlem River to Bronx Park. Fordham Road houses the borough's largest and most diverse shopping district. It geographically separates the North Bronx from the South Bronx.
The Third Avenue Railway System (TARS), founded 1852, was a streetcar system serving the New York City boroughs of Manhattan and the Bronx along with lower Westchester County. For a brief period of time, TARS also operated the Steinway Lines in Long Island City.
The Third and Amsterdam Avenues Line, also known as the Third Avenue Line, is a public transit line in Manhattan, New York City, running from Lower Manhattan to Fort George in Washington Heights. Originally a streetcar line, it now consists of the M98, M101, M102, and M103 bus routes, operated by the New York City Transit Authority. The M98 bus route operates on Third Avenue between East 65th Street and East 127th Street, but formerly continued to 32nd Street. The M101, M102 and M103 bus routes run southbound on Lexington Avenue north of East 24th Street.
The Bx1 and Bx2 are two bus routes that run on the Grand Concourse in the Bronx, New York City. The routes, which are operated by the MTA Regional Bus Operations, also follow Sedgwick Avenue and Mosholu Parkway for a short distance at their northern end. As the numbers suggest, these were the first two bus routes in the Bronx.
The Hub is a major commercial center for the South Bronx, New York. It is located where four roads converge: East 149th Street, and Willis, Melrose and Third Avenues. It is primarily located inside the neighborhood of Melrose but also lines the northern border of Mott Haven.
Jerome Avenue is one of the longest thoroughfares in the New York City borough of the Bronx, New York, United States. The road is 5.6 miles (9.0 km) long and stretches from Concourse to Woodlawn. Both of these termini are with the Major Deegan Expressway which runs parallel to the west. Most of the elevated IRT Jerome Avenue Line runs along Jerome Avenue. The Cross Bronx Expressway interchanges with Jerome and the Deegan. Though it runs through what is now the West Bronx neighborhood, Jerome Avenue is the dividing avenue between nominal and some named "West" and "East" streets in the Bronx; Fifth Avenue, and to a lesser extent, Broadway, also splits Manhattan into nominal "West" and "East" streets.
Webster Avenue is a major north–south thoroughfare in the Bronx, New York City, United States. It stretches for 5.8 miles (9.3 km) from Melrose to Woodlawn. The road starts at the intersection of Melrose Avenue, East 165th Street, Brook Avenue, and Park Avenue in the neighborhood of Melrose, ending at Nereid Avenue in the neighborhood of Woodlawn. There are no subway lines along this thoroughfare, unlike the streets it parallels—Jerome Avenue, The Grand Concourse, and White Plains Road, which all have subway lines —but until 1973, Webster Avenue north of Fordham Road was served by the Third Avenue Elevated, served by the 8 train.
The Bx12 is a public transit line in New York City running along the 207th Street Crosstown Line, within the boroughs of Manhattan and the Bronx. The line runs along 207th Street in Upper Manhattan and along the continuous Fordham Road and Pelham Parkway in the Bronx.
149th Street was a station on the demolished IRT Third Avenue Line in the Bronx, New York City. It was located in "The Hub" in the South Bronx, at the intersection of 149th Street, Third Avenue, Willis Avenue, and Melrose Avenue. Opened as an express station in 1887 and later operating as the line's southern terminus, the station closed in 1973 and was demolished by 1977 due to political pressure in the area.
Fordham Road–190th Street was an express station on the demolished IRT Third Avenue Line in the Bronx, New York City. It was located at Fordham Road and Third Avenue, one block east of Webster Avenue, in the modern location of Fordham Plaza. Opened in 1901, the station was closed in 1973 and demolished in 1977 along with the rest of the Third Avenue Line. No trace of the station exists today.
The Bx15 bus route is a public transit line in New York City that operates on the Third Avenue/125th Street Line between Fordham Plaza in the Bronx and Manhattanville in Manhattan. The full-length route runs along Third Avenue and Willis Avenue in the South Bronx, and along 125th Street in Harlem. On weekdays, some buses run a reduced version of the route between the Hub and Fordham Plaza in the Bronx.
The B99, Bx99, and M99, bus routes were a public transit system in the boroughs of Manhattan, Brooklyn, and the Bronx, New York City, running along many lines of all three boroughs. The routes primarily ran from Midtown Manhattan or West Village to either East New York, Brooklyn; Woodlawn, Bronx; or Midwood, Brooklyn. The three bus routes were created to replace the 2 and 4 trains during the COVID-19 pandemic, when overnight New York City Subway service was suspended between 1:00 AM and 5:00 AM. All three routes overlap in Manhattan.