| Our Lanka (A Play in Three Acts) | H. Sri | Nissanka | N/A | General |
| Our Legislature | J.R. | Weinman | 1947 | Politics |
| Our Money Grows On Our Trees - Scheme For A National Orchid | Upali | Dias | 1990 | General |
| Our People, Our Potential, Our Pride, Celebrating the 26 Distrcts of Sri Lanka | N/A | N/A | 2014 | General |
| Our Place in the Civilization of the Ancient World | K. | Balasingham | 1918 | General |
| Out of Bondage, A Biography, S. Thondaman | T. | Sabaratnam | 1990 | General |
| Out Of His Life & Thought - F.L.Woodward | D.H. | Panditha Gunewardene | N/A | General |
| Out of the Blue, A Guide to the Marine Mammals of Sri Lanka, Southern India & the Maldives | Howard | Martenstyn | 2013 | General |
| Out Out Brief Candle | M. | Chandrasoma | 1981 | Literature |
| Out Steppes the Don | C.C | de Silva | 1966 | General |
| Out-Door Proctor, The - James Cecil Walter Pereira 1881 | Vijaya | Samaraweera | 2000 | General |
| Outlines of Ceylon History | Donald | Obeyesekere | 1999 | History |
| Outsider, The | Jean | Arasanayagam | N/A | Literature |
| P.R.Electoral System of Sri Lanka, The - An Analysis, Quest Vol 27, No 2, 1988 | Vijaya Niranjan | Perera | 1988 | Politics |
| Paddy Production - Incompetence & Knavery | Vernon H. | Gunasekera | 1967 | General |
| Padre Rowlands of Ceylon | R.P. | Butterfield | N/A | General |
| Pageant of Lanka to Celebrate Independence Day - Souvenir | Govt of Ceylon | N/A | 1948 | General |
| Pagoda House - Recollections of Childhood | Alfreda | De Silva | 1990 | General |
| Painting - Archaeological Series, Vol 5 | Nandadeva, Dr | Wijesekera | 1990 | General |
| Paintings of Sri Lanka - Sigiriya | Roland | Silva | 1990 | General |
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