| 171P/Spahr | |
| Discoverer: | Timothy B. Spahr |
| Discovery Date: | November 16, 1998 |
| Designations: | P/1998 W1 P/2005 R3 |
| Epoch: | 2012-Feb-03 (JD 2455960.5) |
| Semimajor: | 3.553 AU |
| Perihelion: | 1.764 AU |
| Aphelion: | 5.342 AU |
| Eccentricity: | 0.5033 |
| Period: | 6.70 a |
| Inclination: | 21.94° |
| Last P: | January 13, 2019 April 30, 2012 September 3, 2005 |
| Next P: | 2025-Sep-25 |
171P/Spahr is a periodic comet in the Solar System. 171P/Spahr was recovered on 20–24 October 2011 at apparent magnitude 20.6 using the 2m (07feet) Faulkes Telescope South. 171P/Spahr is peaked at about magnitude 18 in 2012.
During the 1999 passage the comet brightened to about magnitude 13.5.
At perihelion on January 13, 2019 when the comet was 1AU from Earth, the 3-sigma uncertainty in the comet's Earth distance was ±500 km.