Menntaskólinn í Reykjavík (often abbreviated MR) is the oldest junior college in Reykjavík, Iceland. 

The school traces its origin to 1056, when a school was established in Skáholt, and it remains one of the oldest institutions in Iceland. The school was moved to Reykjavík in 1786, but poor housing conditions forced it to move again in 1805 to Bessastaðir near Reykjavík. In 1846 the school was moved to its current location, and a new building was erected for it in Reykjavík.

Menntaskólinn í Reykjavík offers a four-year course of study. It usually ends with a degree (stúdentspróf) which gives the graduating student the right to advance to an Icelandic university.