Mark Barrowcliffe, also known by his pseudonyms M.D. Lachlan and Mark Alder, is an English writer born on 14 July 1964.

As M.D. Lachlan, he is known for the Wolfsangel series, which draws heavily on Norse mythology, weaving tales of a werewolf trapped in the schemes of the Gods and doomed to be reborn endlessly. The series reflects his return to fantasy after writing his Dungeons and Dragons memoir, The Elfish Gene.

Under the name Mark Alder, he writes the Banners of Blood series, set in an alternate 100 Years War, where angels and devils walk the earth.

Mark Barrowcliffe has also written works such as Girlfriend 44 and Lucky Dog.