Here are the Russian Orthodox saints that start with "J." Their feastdays are included where available.
- Jacob Netsevetov
- Jacob the New Hieromartyr, April 18
- James the Ascetic, January 28 and June 13
- James of Borovichi, May 22
- James the Brother of the Lord, October 23
- James of Kyros, February 6
- James the Disciple of James the New Martyr, November 1
- James the New Martyr, November 1
- James the Persian, November 27
- James the Son of Alpheus, October 9
- James the Son of Zebedee, April 30
- Januarius, January 25
- Jason, March 19
- Jeremias, Martyr in Cilicia, February 16
- Jeremy the Prophet of the Kiev Caves, October 5
- Jerome, Elder of Mt. Athos
- Jesus Christ, December 25, January 1, January 6, February 2, August 6
- Joachim, Father of the Most Holy Theotokos, September 9
- Joasaph of Mt. Athos, October 26
- John, New Martyr, January 6
- John "Big Cap" of Moscow, July 3
- John the Baptist, see John the Forerunner for feastdays
- John the Bulgarian, March 5
- John the Cabinetmaker, February 26
- John the Chozevite, October 3
- John Chrysostom, November 13
- John of Crete, September 15
- John of Damascus, December 4
- John the Faster, September 2
- John the Forerunner, August 29, January 7, June 24
- John the Hesychast, December 3
- John Koulikas, April 4
- John of Kronstadt the Wonderworker, October 19
- John Kukuzelis, October 1
- John of The Ladder, March 30
- John Maximovitch
- John the Merciful, November 4
- John of Moscow, July 3
- John the Much Suffering of the Kiev Caves, July 18
- John the Nafkliros, April 8
- John the New Martyr at Thessalonica, October 21
- John of the Old Lavra, April 20
- John the Persian, May 30
- John Kovsharov of Petrograd, July 31
- John the Prophet, February 6
- John the Romanian
- John of St. Savas Monastery, March 20 and May 16
- John of Shanghai and San Francisco
- John, Son of Sts. Xenophon and Maria, January 26
- John of Svyatagorsk, July 12
- John the Theologian, September 26, May 8
- John Kochurov of Tsarskoye Selo, December 8
- John of Ustiug, May 29
- John Vlasaty the Merciful, September 3
- John of Wallachia, May 12
- John the Young Tailor, December 20
- Jonah of Manchuria, October 20
- Jonah of Novgorod, November 4
- Jonah the Savaite, September 21
- Jordan of Trebizond, February 2
- Joseph of Aleppo, February 4
- Joseph Gerontogiannis, August 6
- Joseph the Ill of the Far Caves, April 4
- Jude the Brother of the Lord, June 19
- Julia the Martyr of Palestine
- Julian, Martyr at Antinoe, January 8
- Julian, February 16
- Juliana of Lazarevo, July 6
- Justin the Philosopher, October 20
- Justina, October 2
- Juvenal, Patriarch of Jerusalem, July 2
Source: http://www.gnisios.narod.ru/lives.html