Glen MacDonough (1870 – March 30, 1924) was an American writer, lyricist and librettist. He was the son of theater manager Thomas B. MacDonough and actress/author Laura Don. Glen MacDonough married Margaret Jefferson in 1896 in Buzzard's Bay, Massachusetts.

MacDonough was born in Brooklyn, New York. He is best-remembered today as the librettist of Victor Herbert's operetta, Babes in Toyland (1903). MacDonough started out as a feature/human interest journalist in New York City, and according to one source (Atlanta Constitution, Feb. 4, 1894), "...four years ago [MacDonough] was a reporter earning 15 to 20 dollars a week...but was rapidly advanced in salary and prominence. In one year on the New York Advertiser, he wrote 1,008 short stories...He [then] determined to abandon journalism and turn to the drama for a livelihood..."

The Prodigal Father (1892) is MacDonough's first work that received any note in reviews of the day. It was a comedy with songs, a form generally called "musical extravaganzas" at the time. His second work, The Algerian (1893), was a collaboration with prominent songwriter Reginald DeKoven. In the 1890s he devoted much time to writing farces and comedies or the book and song lyrics to a string of musical comedies. These musical comedies include Miss Dynamite (1894) and Delmonico's at 6 (1895). MacDonough's name is associated with more than two dozen plays and musical works. Most of them have become obscure with the passage of time, but some—besides Babes in Toyland—are worthy of mention and present certain points of historical interest.

That is: He wrote the lyrics for the operetta, Chris and the Wonderful Lamp (1899), with music by march king John Philip Sousa, a work that undergoes periodic revival even today. MacDonough was also one of the many lyricists called to help out in the first musical production of L. Frank Baum's The Wizard of Oz (1902). Between 1896 and 1909, MacDonough collaborated with Victor Herbert on four other operettas besides Babes in Toyland: The Gold Bug (1896), It Happened in Nordland (1905), Wonderland (1905), and Algeria (1908, revised in 1909 as The Rose of Algeria). MacDonough was also the American adapter of Johann Strauss' last work, Vienna Life (1901), and of Franz Lehár's The Count of Luxembourg (1912). In 1909 he wrote the book for The Midnight Sons. He was one of the nine founding members of ASCAP in 1914.

Glen MacDonough wrote continuously until the year before his death in Stamford, Connecticut, in 1924. His last work was in 1923, Within Four Walls, a play.