The preparation of ultra high purity niobium (UHP-Nb) from commercial starting materials (niobium metal or Nb 2 O 5 ) requires the elimination of all impurities down to the ppm, sub-ppm or even ppb level. This is possible only by application of a complex technology comprising the following essential processing steps: (1) Removal of critical metallic elements (especially Ta and W) which cannot be evaporated by electron beam melting through suitable chemical and/or physical purification methods as: - liquid-liquid extraction of Nb 2 O 5 with MIBK, chlorination of the oxide, distillation of NbCl 5 and thermal decomposition to metallic niobium, - molten salt electrolysis using LiF-NaF-KF melts containing K 2 NbF 7 , - iodination of Nb, distillation of NbI 5 /partial reduction/re-iodination/thermal decomposition to Nb, (2) Removal of volatile impurities by EBM or EBFZM in high or ultra high vacuum, (3) Decarburization by high temperature annealing under low O 2 partial pressure, (4) Removal of H, O and N by UHV degassing at high temperature. The various purification methods developed for ultra purification of Nb are described with special emphasis on investigations carried out to optimize the conditions of liquid-liquid extraction and molten salt electrolysis. Both processing routes allowed to produce Nb with W and Ta impurity concentrations in the ppb range and residual resistivity ratios RRR > 10000 (best value obtained was 90000). The superconductivity of Nb below the transition temperature T c =9.288 K requires a special RRR measuring technique which will be described in the paper.