diff --git a/api/src/shared/domain/constants.js b/api/src/shared/domain/constants.js
index d5aa5ee6934..d11baa5ecac 100644
--- a/api/src/shared/domain/constants.js
+++ b/api/src/shared/domain/constants.js
@@ -12,7 +12,7 @@ const LOCALE = {
   SPANISH_SPOKEN: 'es',
 };
 
-const SUPPORTED_LOCALES = ['en', 'es', 'fr', 'fr-BE', 'fr-FR', 'nl-BE'];
+const SUPPORTED_LOCALES = ['en', 'es', 'fr', 'fr-BE', 'fr-FR', 'nl-BE', 'nl'];
 
 const ORGANIZATION_FEATURE = {
   MISSIONS_MANAGEMENT: {
diff --git a/api/src/shared/infrastructure/i18n/i18n.js b/api/src/shared/infrastructure/i18n/i18n.js
new file mode 100644
index 00000000000..2e0dd8eaae3
--- /dev/null
+++ b/api/src/shared/infrastructure/i18n/i18n.js
@@ -0,0 +1,54 @@
+import path from 'node:path';
+
+import { I18n } from 'i18n';
+
+import { SUPPORTED_LOCALES } from '../../domain/constants.js';
+import { logger } from '../utils/logger.js';
+
+const __dirname = import.meta.dirname;
+const translationsFolder = path.resolve(path.join(__dirname, '../../../../translations'));
+
+const supportedLocales = SUPPORTED_LOCALES.map((supportedLocale) => supportedLocale.toLowerCase());
+
+const DEFAULT_LOCALE = 'fr';
+
+export const options = {
+  locales: ['en', 'fr', 'es', 'nl'],
+  fallbacks: { 'en-*': 'en', 'fr-*': 'fr', 'es-*': 'es', 'nl-*': 'nl' },
+  defaultLocale: DEFAULT_LOCALE,
+  directory: translationsFolder,
+  queryParameter: 'lang',
+  languageHeaderField: 'Accept-Language',
+  objectNotation: true,
+  updateFiles: false,
+  mustacheConfig: {
+    tags: ['{', '}'],
+    disable: false,
+  },
+};
+
+// This is an optimization to avoid settings a new instance each time
+// we need to use i18n.
+const i18nInstances = {};
+
+/**
+ * @param {string} locale a locale (language or BCP 47 format)
+ * @returns i18n instance correctly setup with the language
+ */
+export function getI18n(locale) {
+  if (!locale || !supportedLocales.includes(locale?.toLowerCase())) {
+    return getI18n(DEFAULT_LOCALE);
+  }
+
+  if (!i18nInstances[locale]) {
+    const i18n = new I18n(options);
+    i18n.setLocale(locale);
+    // we freeze the setLocale to avoid changing i18n locale for an instance
+    i18n.setLocale = () => {
+      logger.warn('Cannot change i18n locale instance, use getI18n(locale) instead.');
+    };
+    i18nInstances[locale] = i18n;
+  }
+
+  return i18nInstances[locale];
+}
diff --git a/api/src/shared/infrastructure/plugins/i18n.js b/api/src/shared/infrastructure/plugins/i18n.js
index 7c23140c6e8..5e140e6e9c8 100644
--- a/api/src/shared/infrastructure/plugins/i18n.js
+++ b/api/src/shared/infrastructure/plugins/i18n.js
@@ -1,20 +1,7 @@
-import * as url from 'node:url';
-
 import hapiI18n from 'hapi-i18n';
-const __dirname = url.fileURLToPath(new URL('.', import.meta.url));
+
+import { options } from '../i18n/i18n.js';
+
 const plugin = hapiI18n;
-const options = {
-  locales: ['en', 'fr', 'es', 'nl'],
-  directory: __dirname + '../../../../translations',
-  defaultLocale: 'fr',
-  queryParameter: 'lang',
-  languageHeaderField: 'Accept-Language',
-  objectNotation: true,
-  updateFiles: false,
-  mustacheConfig: {
-    tags: ['{', '}'],
-    disable: false,
-  },
-};
 
 export { options, plugin };
diff --git a/api/tests/shared/unit/infrastructure/i18n/i18n_test.js b/api/tests/shared/unit/infrastructure/i18n/i18n_test.js
new file mode 100644
index 00000000000..4bb8f4f26c7
--- /dev/null
+++ b/api/tests/shared/unit/infrastructure/i18n/i18n_test.js
@@ -0,0 +1,59 @@
+import { getI18n, options } from '../../../../../src/shared/infrastructure/i18n/i18n.js';
+import { expect } from '../../../../test-helper.js';
+
+describe('Unit | Shared | Infrastucture | i18n', function () {
+  describe('default i18n options', function () {
+    it('returns i18n options', function () {
+      expect(options).to.have.property('locales').that.includes('en', 'fr', 'es', 'nl');
+      expect(options).to.have.property('directory').that.is.a('string');
+      expect(options).to.have.property('defaultLocale', 'fr');
+      expect(options).to.have.property('queryParameter', 'lang');
+      expect(options).to.have.property('languageHeaderField', 'Accept-Language');
+      expect(options).to.have.property('objectNotation', true);
+      expect(options).to.have.property('updateFiles', false);
+      expect(options)
+        .to.have.property('mustacheConfig')
+        .to.deep.equal({
+          tags: ['{', '}'],
+          disable: false,
+        });
+    });
+  });
+
+  describe('getI18n', function () {
+    it('returns an instance of i18n with default locale', function () {
+      const i18n = getI18n();
+      expect(i18n.getLocale()).to.equal('fr');
+    });
+
+    it('returns an instance of i18n with the specified locale', function () {
+      const locale = 'es';
+      const i18n = getI18n(locale);
+      expect(i18n.getLocale()).to.equal(locale);
+    });
+
+    context('when the locale is BCP 47 format', function () {
+      it('returns the correct locale instance of i18n', function () {
+        const locale = 'nl-BE';
+        const i18n = getI18n(locale);
+        expect(i18n.getLocale()).to.equal('nl');
+      });
+    });
+
+    context('when the locale is not supported', function () {
+      it('returns the default locale instance of i18n', function () {
+        const locale = 'foo';
+        const i18n = getI18n(locale);
+        expect(i18n.getLocale()).to.equal('fr');
+      });
+    });
+
+    context('when the i18n setLocale is called on an i18n instance', function () {
+      it('does not change the instance locale', function () {
+        const i18n1 = getI18n('fr');
+        i18n1.setLocale('en');
+        expect(i18n1.getLocale()).to.equal('fr');
+      });
+    });
+  });
+});
diff --git a/api/tests/tooling/i18n/i18n.js b/api/tests/tooling/i18n/i18n.js
deleted file mode 100644
index 55e1c607e54..00000000000
--- a/api/tests/tooling/i18n/i18n.js
+++ /dev/null
@@ -1,20 +0,0 @@
-import path from 'node:path';
-import * as url from 'node:url';
-
-import { I18n } from 'i18n';
-
-import { options } from '../../../src/shared/infrastructure/plugins/i18n.js';
-const __dirname = url.fileURLToPath(new URL('.', import.meta.url));
-
-function getI18n() {
-  const directory = path.resolve(path.join(__dirname, '../../../translations'));
-
-  const i18n = new I18n();
-  i18n.configure({
-    ...options,
-    directory,
-  });
-  return i18n;
-}
-
-export { getI18n };
diff --git a/api/tests/tooling/i18n/i18n_test.js b/api/tests/tooling/i18n/i18n_test.js
deleted file mode 100644
index 3cacd02d2ca..00000000000
--- a/api/tests/tooling/i18n/i18n_test.js
+++ /dev/null
@@ -1,9 +0,0 @@
-import { expect } from '../../test-helper.js';
-import { getI18n } from './i18n.js';
-
-describe('Unit | Tooling | i18n', function () {
-  it('should translate by default to fr', function () {
-    const currentLang = getI18n().getLocale();
-    expect(currentLang).to.equal('fr');
-  });
-});