Reel-to-reel audio tape recording, also called open-reel recording, is magnetic tape audio recording in which the recording tape is spooled between reels. To prepare for use, the supply reel (or feed reel) containing the tape is placed on a spindle or hub. The end of the tape is manually pulled from the reel, threaded through mechanical guides and over a tape head assembly, and attached by friction to the hub of the second, initially empty take-up reel. Reel-to-reel systems use tape that is 1⁄4, 1⁄2, 1, or 2 inches (6.35, 12.70, 25.40, or 50.80 mm) wide, which normally moves at 3+3⁄4, 7+1⁄2, 15 or 30 inches per second (9.525, 19.05, 38.10 or 76.20 cm/s). Domestic consumer machines almost always used 1⁄4 inch (6.35 mm) or narrower tape and many offered slower speeds such as 1+7⁄8 inches per second (4.762 cm/s). All standard tape speeds are derived as a binary submultiple of 30 inches per second.

Reel-to-reel preceded the development of the compact cassette with tape 0.15 inches (3.8 mm) wide moving at 1+7⁄8 inches per second (4.8 cm/s). By writing the same audio signal across more tape, reel-to-reel systems give much greater fidelity at the cost of much larger tapes. In spite of the relative inconvenience and generally more expensive media, reel-to-reel systems developed in the early 1940s remained popular in audiophile settings into the 1980s and have re-established a specialist niche in the 21st century.

Studer, Stellavox, Tascam, and Denon produced reel-to-reel tape recorders into the 1990s, but as of 2017, only Mechlabor continues to manufacture analog reel-to-reel recorders. As of 2020, there were two companies manufacturing magnetic recording tape: ATR Services of York, Pennsylvania, and Recording the Masters in Avranches, France.

Reel-to-reel tape was used in early tape drives for data storage on mainframe computers and in video tape recorders. Magnetic tape was also used to record data signals from analytical instruments, beginning with the hydrogen bomb testing of the early 1950s.