Bhikkhu Nyānadassana Mahāthera (born 1959, Serres) is a Theravāda Greek Buddhist monk, scholar, and teacher.
Early life and education.
Bhikkhu Nyānadassana Mahāthera was born Ioannis Tselios () in 1959 in Karperi, Serres, Greece, and completed his high school education in Thessaloniki. He studied sociology at the Goethe University in Frankfurt, Germany for two years but left before completing his degree.
Ioannis Tselios traveled around South Asia during the 1980s. He first went to India in 1981 and visited key Buddhist sites, including Kushinagar and Lumbini. Later on, he traveled to Sri Lanka.
Monastic life.
In 1982, Ioannis Tselios received novice ordination ("sāmaṇera") in Sri Lanka at the Polgasduwa Island Hermitage, where he was given the monastic name "Nyānadassana", meaning "knowledge and vision." A month later, he renewed his novice ordination at Galduwa, with Kaḍaveddūve Shrī Jinavaṁsa Mahāthera officiating as his preceptor. In 1986, he was fully ordained as a bhikkhu under the same preceptor.
For sixteen years, he studied Pali, the Tipiṭaka (Buddhist Triple Canon), and commentarial literature at the Gnānārāma Dharmāyatanaya monastery in Mītirigala. In 1997, he earned the title of "Vinayācariya" (Teacher of Monastic Discipline) after completing rigorous examinations. Inspired by his teacher, he began teaching the Pāḷi language and the Tipiṭaka for several years.
Meditation.
Nyānadassana has devoted decades to meditative practices, including Vipassanā (insight meditation) and Samatha (concentration meditation). He practised at Nissaraṇa Vanaya in Mītirigala, Sri Lanka, under the guidance of the renowned meditation teacher Venerable Mātara Sri Ñāṇārāma Mahāthera. and spent over three years at the Pa-Auk Meditation Centre in Myanmar, receiving training under Pa-Auk Sayadaw.
Between 2008 and 2018, he was regularly invited by Buddhist centres in Singapore, Indonesia, Malaysia, and Taiwan to deliver Dhamma talks and meditation classes. From 2011 to 2019, he resided at Nā Uyana Forest Monastery and International Meditation Centre in Kurunegala, Sri Lanka.
Return to Greece.
In 2019, Nyānadassana Mahāthera received an invitation to teach Theravāda Buddhism in Greece from Michail Xynos, who at the time was directing the Theravada Centre for Study and Practice in Greece. From 2019 until 2025, he conducted extensive courses in Buddhist philosophy and psychology in Greek, along with live and online meditation seminars for Greek, Sri Lankan, European, and Asian audiences.
During this period, he authored several books.
Publications.
Nyānadassana Mahāthera has authored and translated numerous works in multiple languages, including English, German, Greek, and Sinhala. His publications include: