Is “1 EUR” in Russian  Одно евро, Одна евро or Один евро ???

                                                                                                        

The answer:   Один евро  [ᴧd-EE-n    yEvrᴧ] - 1 EUR

 

евро  [yEvrᴧ] is a masculine noun, in spite of having the attributes of a neuter noun - ending -о

For example, the words Кино [k-ee-nO] - cinema, Пальто [pᴧl'tO] - a coat, Окно [ᴧknO] - a window end in -O and are the nouns of neuter gender.

You might hear that somebody saying - Одно евро - following the general rule: if a noun ends in -o it's a neuter noun.

There are even examples of using евро as a feminine noun: Одна евро - the argument being that евро is валюта [vᴧl-OO-tᴧ] - currency, therefore should be feminine because the word валюта [vᴧl-OO-tᴧ] is feminine. 

Both examples are wrong - Евро is a masculine noun and follows the same rules as Рубль [r-oo-bl'] - rouble or Доллар [dOlᴧr] - dollar.
Один рубль  [ᴧd-EE-n   r-oo-bl']  -  1  rouble

Один доллар [ᴧd-EE-n   dolᴧr] - 1 dollar

Один евро [ᴧd-EE-n    yEvrᴧ] - 1 euro

However unlike Рубль [r-oo-bl'] - rouble or Доллар [dOlᴧr] - dollar, Евро doesn't decline, it doesn't change in different cases, that actually makes it much easier to use, you don't need to think what ending to use say in the Accusative Case Plural.

Singular Nominitive case	Оди́н рубль - 1 rouble	Оди́н доллар – 1 $	Оди́н е́вро – 1 EUR
Plural Nominative case	Два рубля́  - 2 roubles [dvA  r-oo-blyA]	Три до́ллара – 3 $ [tr-ee-  dOlᴧrᴧ]	Четы́ре е́вро – 4 EUR [ch-ee-tir-ee  yEvrᴧ]
Plural Genitive case	Двух рубле́й [dv-oo-h   r-oo-blEy]	Трёх до́лларов [tryOh  dOlᴧrᴧv]	Четырёх е́вро [ch-ee-tiryOh  yEvrᴧ]
Plural Dative case	Дву́м рубля́м [dv-oo-m   r-oo-blyAm]	Трём до́лларам [tryOm  dOlᴧrᴧm]	Четырём е́вро [ch-ee-tiryOm  yEvrᴧ]