| CAI (1) m Scandinavian |
| CAJ m Scandinavian |
| CLAES m Swedish |
| CLAUS m German, Danish |
| COL m Medieval English |
| COLETTE f French |
| COLIN (2) m English |
| COLINE f French |
| COLLIN m English |
| KAI (1) m Frisian, German, Scandinavian, Finnish, Dutch |
| KAJ (1) m Scandinavian |
| KAY (3) m Frisian, German, Scandinavian |
| KLAAS m German, Dutch |
| KLAES m Frisian |
| KLAOS m Limburgish |
| KLAS m Swedish |
| KLASINA f Dutch |
| KLAUS m German, Danish, Norwegian, Finnish |
| KLAZINA f Dutch |
| KOLYA m Russian |
| LAUNO m Finnish (Rare) |
| MIKLAVŽ m Slovene |
| MIKLÓS m Hungarian |
| MIKOŁAJ m Polish |
| MIKOLÁŠ m Czech |
| MIKULA m Czech |
| MIKULÁŠ m Slovak, Czech |
| MYKOLA m Ukrainian |
| NEACEL m Scottish |
| NECULAI m Romanian |
| NELS m Swedish (Rare) |
| NIC m English |
| NICCOLÒ m Italian |
| NICHOL m Scottish |
| NICHOLA f English (British) |
| NICHOLAS m English, French |
| NICHOLE f English |
| NIĈJO m Esperanto |
| NICK m English, Dutch |
| NICKOLAS m English |
| NICKOLAUS m German |
| NICKY m & f English |
| NICO m Italian, Dutch, German, Spanish, Portuguese |
| NICOL m Scottish |
| NICOLA (1) m Italian |
| NICOLA (2) f English (British) |
| NICOLAAS m Dutch |
| NICOLAE m Romanian |
| NICOLAO m Spanish |
| NICOLAOS m Greek |
| NICOLÁS m Spanish |
| NICOLAS m French |
| NICOLASA f Spanish |
| NICOLAU m Portuguese, Galician, Catalan |
| NICOLAUS m German, Ancient Greek (Latinized) |
| NICOLE f French, English, Dutch |
| NICOLET f Dutch |
| NICOLETA f Romanian |
| NICOLETTA f Italian |
| NICOLETTE f French |
| NICOLINA f Italian |
| NICOLINE f French, Dutch |
| NICOLÒ m Italian |
| NICU m Romanian |
| NICUȘOR m Romanian |
| NIEK m Dutch |
| NIELS (1) m Danish |
| NIGUL m Estonian |
| NIILO m Finnish |
| NIK m Slovene |
| NIKA (2) f Slovene, Croatian |
| NIKICA m Croatian, Serbian |
| NIKKI f English |
| NIKKOLE f English (Rare) |
| NIKLAS m Swedish, Finnish |
| NIKLAUS m German (Swiss) |
| NIKO m Finnish, Croatian, Slovene |
| NIKOL f Czech |
| NIKOLA (1) m Serbian, Croatian, Slovene, Bulgarian, Macedonian, Hungarian, Czech, Basque, Medieval Slavic |
| NIKOLA (2) f German, Polish, Czech, Slovak |
| NIKOLAAS m Dutch |
| NIKOLAI m Russian, Bulgarian |
| NIKOLAJ m Danish, Slovene |
| NIKOLAJS m Latvian |
| NIKOLAO m Esperanto |
| NIKOLAOS m Ancient Greek, Greek |
| NIKOLAS m English, Greek |
| NIKOLAUS m German, Scandinavian (Rare), Finnish (Rare) |
| NIKOLCHE m Macedonian |
| NIKOLE f Basque, English |
| NIKOLETA f Greek |
| NIKOLETT f Hungarian |
| NIKOLINA f Bulgarian, Croatian, Serbian, Macedonian |
| NIKOLOZ m Georgian |
| NIKŠA m Croatian |
| NILS m Swedish, Norwegian |
| NIOCLÁS m Irish |
