| Mountain of Black Glass | |
| Author: | Tad Williams |
| Cover Artist: | Michael Whelan |
| Country: | United States |
| Language: | English |
| Series: | Otherland |
| Publisher: | DAW Books / Donald A. Wollheim |
| Release Date: | September 1, 1999 |
| Media Type: | Print (hardback & paperback) |
| Pages: | 720 (Hardback) |
| Isbn: | 0-88677-849-2 |
| Isbn Note: | (Hardback) |
| Dewey: | 813/.54 21 |
| Congress: | PS3573.I45563 M68 1999 |
| Oclc: | 42085452 |
| Preceded By: | River of Blue Fire |
| Followed By: | Sea of Silver Light |
Mountain of Black Glass is a science fiction novel by American writer Tad Williams, the third book in his Otherland series. It was first published in 1999 with a paperback edition in 2000.
Continuing from River of Blue Fire it brings the characters together at the battle of Troy and finally to the heart of the Grail Brotherhood.