Interstate 787 (I-787) is an auxiliary Interstate Highway in the US state of New York. I-787 is the main highway for those traveling into and out of downtown Albany. The southern terminus is, per New York traffic data, at New York State Thruway (I-87) exit 23 southwest of downtown Albany. However, current signage indicates the terminus as along I-787's ramp to US Route 9W (US 9W). The northern terminus of the route is unclear, with some sources placing the terminus at 8th Street in Troy, creating an overlap with New York State Route 7 (NY 7) between Green Island and Troy. Other documents show I-787 as terminating at its interchange with NY 7 and NY 787 in the town of Colonie. Regardless, the route is 10.16 miles (16.35 km) long if extended to Troy, or 9.55 miles (15.37 km) excluding the unsigned NY 7 overlap.

North of NY 7, I-787 continues north as NY 787 to the city of Cohoes.

I-787 officially begins at the US 9W exit (formerly a toll barrier for I-87/Thruway exit 23); however, a short 0.57-mile (0.92 km) spur between US 9W and the interchange connecting I-787 to the Thruway, designated as New York State Route 912S (NY 912S), an unsigned reference route, is signed as I-787. At the east end of the interchange (exit 1) with I-87, I-787 northbound merges with NY 912S, progressing due east for a short distance before curving to the northeast ahead of the Delaware and Hudson Railway mainline near exit 2 (NY 32). Past NY 32, I-787 parallels the Hudson River as it heads northward into the heart of downtown Albany, featuring a pair of exits with US 9 and US 20 at a massive interchange southeast of the Empire State Plaza on the west bank of the Hudson.

North of downtown Albany, I-787 interchanges with I-90 at exit 5 prior to crossing into Menands and meeting NY 32 once more at exit 6 by way of a trumpet interchange. The ramp from the trumpet to NY 32, a 0.28-mile-long (0.45 km) roadway, is designated as unsigned NY 913T. Farther north in Menands, I-787 intersects NY 378 (exit 7) by way of a partial cloverleaf interchange. In Watervliet, I-787 has one interchange with 23rd Street (exit 8) before reaching another partial cloverleaf interchange with NY 7 and NY 787 (exit 9) in Green Island.

I-787's alignment after exit 9 is unclear. Appendix E of the 2008 New York State Department of Transportation (NYSDOT) Traffic Data Report places the terminus at 8th Street in Troy, creating an overlap with NY 7 across the Hudson River via the Collar City Bridge. Additionally, there are shields for I-787 on the Collar City Bridge east of the Hudson River, and the bridge’s roadway uses I-787 reference markers instead of NY 7. Other sources, including the National Highway System map of Albany published by the Federal Highway Administration (FHWA) and NYSDOT's official description of signed routes in New York State, identifies the terminus as the NY 7/NY 787 interchange near Green Island. Contemporary maps of the Albany area also lack I-787 shields on the Collar City Bridge, signing the roadway only as NY 7.

According to NYSDOT traffic counts, I-787 is 10.16 miles (16.35 km) long; by limiting I-787 to the section between the Thruway and NY 7, the length is reduced to 9.55 miles (15.37 km).

Construction began in the early 1960s on the first segment of I-787 from I-87 to Bassett Street. It was completed and opened to traffic in the mid-1960s. By 1968, construction had begun on the remainder of I-787 south of Watervliet. The portion of the highway between I-90 and NY 378 was completed by 1971; the rest of I-787 south of 23rd Street in Watervliet was built and open to traffic by 1973. The ramps from the South Mall Arterial were opened in 1974. An extension of the freeway north to Arch Street near Green Island was completed by 1977. By 1980, the majority of modern exit 9 was completed even though the Collar City Bridge and the "Alternate Route 7" freeway had yet to be constructed. The Collar City Bridge over the Hudson River was built in 1981, connecting the preexisting ramps at exit 9 to downtown Troy.

When I-787 was first planned, its northern terminus was at US 4 in Troy. On January 1, 1970, the I-787 designation was truncated westward to what is now exit 9 near Green Island while the then-proposed Collar City Bridge became (albeit on paper) part of I-88, a new highway extending from Binghamton to Troy by way of the Susquehanna Expressway and Alternate Route 7. The extension of I-88 never materialized as Alternate Route 7 ended up becoming a realignment of NY 7 when it was completed in the 1980s.