Here are the Russian Orthodox saints that start with the letter "M," with their feastdays where possible:
- Macarios the New Martyr at Constantinople, October 6
- Macarios the New Martyr at Thessalonica, September 14
- Macarius of Alexandria, January 19
- Macarius, Faster of Pechersk, January 19
- Macarius the Great of Egypt
- Macarius of Oredezh, February 9
- Macarius the Roman, January 19 and August 15
- Macrina the Younger, July 19
- Macrobius of Sythopolis, May 4
- Makary the Deacon of the Far Caves, January 19
- Makary the Unmercenary of the Far Caves, December 13
- Malachi, January 3
- Mamas of Caesarea, September 2
- Manetha of Caesarea, November 13
- Manuel the Cretan, March 15
- Marcella of Chios, July 22
- Marcia, Virgin Martyr of Palestine, July 6
- Marcian of Cyr, January 18
- Marcian the Presbyter, January 10
- Marcionilla, January 8
- Maria of Constantinople, January 26
- Maria of Methymopoula, May 1 or 3
- Marianus, March 19
- Marina, February 28
- Marina and Kira
- Marina the Martyr of Pisidian Antioch
- Marinus the Soldier and Asterius the Senator the Martyrs
- Mark the Cave Dweller of the Kiev Caves, December 29
- Mark of Crete, May 14
- Mark of Ephesus, January 19
- Mark the Evangelist, April 25
- Martha, Virgin Martyr of Palestine, June 6
- Martha, Abbess of Pskov, November 8
- Martialis, January 25
- Martin of Tours
- Martinian
- Martiry of the Far Caves, October 25
- Martyrius of Zelenetsk, March 1
- Mary, the Most Holy Theokotos, March 25, August 15, September 8, November 21
- Mary of Egypt, April 1]
- Mary Magdalene, equal to the Apostles, July 22
- Mary of Palestine, September 29
- Mary, Virgin Martyr of Palestine, June 6
- Mary Golinduc of Persia, July 13
- Mary of Thrace, December 26
- Mary-Marinus, February 12
- Mastridia of Jerusalem, February 7
- Matrona the Wise of Chios, October 20
- Matthew the Apostle, November 16
- Matthew the Prophet of the Kiev Caves, October 5
- Matthias the Apostle, August 9
- Maurus, March 19
- Maximos the Confessor, also known as Maximus the Confessor, January 21
- Maximus of Moscow, November 11
- Maximus the New, January 18
- Maximus of Totma, January 16
- Melanie the Younger, December 31
- Melda of Scythopolis, also known as Melous of Scyothopolis May 4
- Meletius, February 12
- Merkury of the Far Caves, July 19
- Micah of Radonezh, May 6
- Micaiah, January 5
- Michael the Archangel
- Michael the Confessor, December 18
- Michael the Gardener, June 30
- Michael of Klopsk, January 11
- Michael of Vourla, April 16
- Michael the Prelate of Kiev
- Michael the Prince
- Michael of St. Savas Lavra, May 23
- Militza the Queen of Serbia
- Mitrophan of Voronezh, November 23
- Mitrophan Manuilov
- Modestus I, December 18
- Modestus II, December 16
- Monica of the North Africa
- Moses the Hungarian of the Kiev Caves, July 26
- Moses the Wonderworker of the Far Caves, July 29
- Myron of Crete, March 20
- Myrope, December 2
Source: http://www.gnisios.narod.ru/lives.html