diff --git a/C4/Languages.pm b/C4/Languages.pm
index e84aa1418a..61898c911f 100644
--- a/C4/Languages.pm
+++ b/C4/Languages.pm
@@ -28,6 +28,7 @@ use List::MoreUtils qw( any );
 use C4::Context;
 use Koha::Caches;
 use Koha::Cache::Memory::Lite;
+use Koha::Language;
 
 our (@ISA, @EXPORT_OK);
 BEGIN {
@@ -111,12 +112,17 @@ Returns a reference to an array of hashes:
 =cut
 
 sub getTranslatedLanguages {
-    my ($interface, $theme, $current_language, $which) = @_;
+    my ($interface, $theme, $current_language) = @_;
     my @languages;
-    my @enabled_languages =
-      ( $interface && $interface eq 'intranet' )
-      ? split ",", C4::Context->preference('StaffInterfaceLanguages')
-      : split ",", C4::Context->preference('OPACLanguages');
+
+    my @enabled_languages;
+    if ($interface) {
+        if ($interface eq 'intranet') {
+            @enabled_languages = split ",", C4::Context->preference('StaffInterfaceLanguages');
+        } elsif ($interface eq 'opac') {
+            @enabled_languages = split ",", C4::Context->preference('OPACLanguages');
+        }
+    }
 
     my $cache = Koha::Caches->get_instance;
     my $cache_key = "languages_${interface}_${theme}";
@@ -640,8 +646,26 @@ sub accept_language {
 
 =head2 getlanguage
 
-    Select a language based on the URL parameter 'language', a cookie,
-    syspref available languages & browser
+Select a language based on:
+
+=over
+
+=item * the URL parameter 'language' (staff and opac interfaces only),
+
+=item * the 'KohaOpacLanguage' cookie (staff and opac interfaces only),
+
+=item * the language set by C<Koha::Language::set_requested_language>
+(interfaces other than staff and opac only). The REST API sets this to the
+value of 'KohaOpacLanguage' cookie,
+
+=item * syspref StaffInterfaceLanguages (staff only)
+
+=item * syspref OpacLanguages (opac only),
+
+=item * HTTP header Accept-Language (more precisely, environment variable
+HTTP_ACCEPT_LANGUAGE)
+
+=back
 
 =cut
 
@@ -655,29 +679,36 @@ sub getlanguage {
         return $cached if $cached;
     }
 
-    $cgi //= CGI->new;
     my $interface = C4::Context->interface;
-    my $theme = C4::Context->preference( ( $interface eq 'opac' ) ? 'opacthemes' : 'template' );
+    my $theme = '';
     my $language;
-
-    my $preference_to_check =
-      $interface eq 'intranet' ? 'StaffInterfaceLanguages' : 'OPACLanguages';
-    # Get the available/valid languages list
     my @languages;
-    my $preference_value = C4::Context->preference($preference_to_check);
-    if ($preference_value) {
-        @languages = split /,/, $preference_value;
-    }
 
-    # Chose language from the URL
-    my $cgi_param_language = $cgi->param( 'language' );
-    if ( defined $cgi_param_language && any { $_ eq $cgi_param_language } @languages) {
-        $language = $cgi_param_language;
-    }
+    if ($interface eq 'opac' || $interface eq 'intranet') {
+        $cgi //= CGI->new;
+        $theme = C4::Context->preference( ( $interface eq 'opac' ) ? 'opacthemes' : 'template' );
 
-    # cookie
-    if (not $language and my $cgi_cookie_language = $cgi->cookie('KohaOpacLanguage') ) {
-        ( $language = $cgi_cookie_language ) =~ s/[^a-zA-Z_-]*//; # sanitize cookie
+        my $preference_to_check =
+          $interface eq 'intranet' ? 'StaffInterfaceLanguages' : 'OPACLanguages';
+        # Get the available/valid languages list
+        my $preference_value = C4::Context->preference($preference_to_check);
+        if ($preference_value) {
+            @languages = split /,/, $preference_value;
+        }
+
+        # Chose language from the URL
+        my $cgi_param_language = $cgi->param( 'language' );
+        if ( defined $cgi_param_language && any { $_ eq $cgi_param_language } @languages) {
+            $language = $cgi_param_language;
+        }
+
+        # cookie
+        if (not $language and my $cgi_cookie_language = $cgi->cookie('KohaOpacLanguage') ) {
+            ( $language = $cgi_cookie_language ) =~ s/[^a-zA-Z_-]*//; # sanitize cookie
+        }
+    } else {
+        @languages = map { $_->{rfc4646_subtag} } @{ getTranslatedLanguages($interface, $theme) };
+        $language = Koha::Language->get_requested_language();
     }
 
     # HTTP_ACCEPT_LANGUAGE
diff --git a/Koha/App/Intranet.pm b/Koha/App/Intranet.pm
index 558de8da1c..5628174fdc 100644
--- a/Koha/App/Intranet.pm
+++ b/Koha/App/Intranet.pm
@@ -39,6 +39,7 @@ sub startup {
     $self->plugin('RESTV1');
 
     $self->plugin('CSRF');
+    $self->plugin('Language');
 
     $self->hook(before_dispatch => \&_before_dispatch);
     $self->hook(around_action => \&_around_action);
diff --git a/Koha/App/Opac.pm b/Koha/App/Opac.pm
index 1f722360e4..d41a704776 100644
--- a/Koha/App/Opac.pm
+++ b/Koha/App/Opac.pm
@@ -39,6 +39,7 @@ sub startup {
     $self->plugin('RESTV1');
 
     $self->plugin('CSRF');
+    $self->plugin('Language');
 
     $self->hook(before_dispatch => \&_before_dispatch);
     $self->hook(around_action => \&_around_action);
diff --git a/Koha/App/Plugin/Language.pm b/Koha/App/Plugin/Language.pm
new file mode 100644
index 0000000000..c93e4fa95f
--- /dev/null
+++ b/Koha/App/Plugin/Language.pm
@@ -0,0 +1,72 @@
+package Koha::App::Plugin::Language;
+
+# This file is part of Koha.
+#
+# Koha is free software; you can redistribute it and/or modify it
+# under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# Koha is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Koha; if not, see <http://www.gnu.org/licenses>.
+
+=head1 NAME
+
+Koha::App::Plugin::Language
+
+=head1 SYNOPSIS
+
+    $app->plugin('Language');
+
+=head1 DESCRIPTION
+
+Sets the current language based on request (cookies, headers, ...)
+
+=cut
+
+use Modern::Perl;
+
+use Mojo::Base 'Mojolicious::Plugin';
+
+use Koha::Language;
+
+=head1 METHODS
+
+=head2 register
+
+Called by Mojolicious when the plugin is loaded.
+
+Defines an `around_action` hook that will sets the current language based on
+the current request.
+
+=cut
+
+sub register {
+    my ( $self, $app, $conf ) = @_;
+
+    $app->hook(
+        around_action => sub {
+            my ( $next, $c, $action, $last ) = @_;
+
+            # Make the value of Accept-Language header and KohaOpacLanguage
+            # cookie accessible to C4::Languages::getlanguage when not in a CGI
+            # context
+
+            if ( my $accept_language = $c->req->headers->accept_language ) {
+                $ENV{HTTP_ACCEPT_LANGUAGE} = $accept_language;
+            }
+            if ( my $KohaOpacLanguage = $c->cookie('KohaOpacLanguage') ) {
+                Koha::Language->set_requested_language($KohaOpacLanguage);
+            }
+
+            return $next->();
+        }
+    );
+}
+
+1;
diff --git a/Koha/Language.pm b/Koha/Language.pm
new file mode 100644
index 0000000000..1dcb58237e
--- /dev/null
+++ b/Koha/Language.pm
@@ -0,0 +1,46 @@
+package Koha::Language;
+
+=head1 NAME
+
+Koha::Language
+
+=head1 SYNOPSIS
+
+    use Koha::Language;
+
+    Koha::Language->set_requested_language('xx-XX');
+    my $language = Koha::Language->get_requested_language();
+
+=head1 DESCRIPTION
+
+This module is essentially a communication tool between the REST API and
+C4::Languages::getlanguage so that getlanguage can be aware of the value of
+KohaOpacLanguage cookie when not in CGI context.
+
+It can also be used in other contexts, like command line scripts for instance.
+
+=cut
+
+use Modern::Perl;
+
+use Koha::Cache::Memory::Lite;
+
+use constant REQUESTED_LANGUAGE_CACHE_KEY => 'requested_language';
+
+sub set_requested_language {
+    my ($class, $language) = @_;
+
+    my $cache = Koha::Cache::Memory::Lite->get_instance;
+
+    $cache->set_in_cache(REQUESTED_LANGUAGE_CACHE_KEY, $language);
+}
+
+sub get_requested_language {
+    my ($class) = @_;
+
+    my $cache = Koha::Cache::Memory::Lite->get_instance;
+
+    return $cache->get_from_cache(REQUESTED_LANGUAGE_CACHE_KEY);
+}
+
+1;
diff --git a/Koha/REST/V1.pm b/Koha/REST/V1.pm
index 52bd15697e..1a3559bfdf 100644
--- a/Koha/REST/V1.pm
+++ b/Koha/REST/V1.pm
@@ -153,6 +153,7 @@ sub startup {
         $self->app->log->warn( "Warning: Failed to fetch oauth configuration: " . $_ );
     };
 
+    $self->plugin('Koha::App::Plugin::Language');
     $self->plugin('Koha::REST::Plugin::Pagination');
     $self->plugin('Koha::REST::Plugin::Query');
     $self->plugin('Koha::REST::Plugin::Objects');
diff --git a/Koha/REST/V1/Auth.pm b/Koha/REST/V1/Auth.pm
index c10e81cf8a..dd59def5f1 100644
--- a/Koha/REST/V1/Auth.pm
+++ b/Koha/REST/V1/Auth.pm
@@ -155,11 +155,6 @@ sub authenticate_api_request {
     $c->stash_embed( { spec => $spec } );
     $c->stash_overrides();
 
-    # FIXME: Remove once CGI is not used
-    my $accept_language = $c->req->headers->accept_language;
-    $ENV{HTTP_ACCEPT_LANGUAGE} = $accept_language
-        if $accept_language;
-
     my $cookie_auth = 0;
 
     my $authorization = $spec->{'x-koha-authorization'};
diff --git a/t/Languages.t b/t/Languages.t
index 14c5d2866d..4b13d02cc2 100755
--- a/t/Languages.t
+++ b/t/Languages.t
@@ -18,10 +18,11 @@
 # with Koha; if not, see <http://www.gnu.org/licenses>.
 
 use Modern::Perl;
-use Test::More tests => 4;
+use Test::More tests => 5;
 use Test::MockModule;
 use CGI qw ( -utf8 );
 use Koha::Cache::Memory::Lite;
+use Koha::Language;
 
 BEGIN {
     use_ok('C4::Languages', qw( getlanguage ));
@@ -32,6 +33,7 @@ my @languages = (); # stores the list of active languages
 my $return_undef = 0;
 
 my $module_context = Test::MockModule->new('C4::Context');
+my $module_languages = Test::MockModule->new('C4::Languages');
 
 $module_context->mock(
     preference => sub {
@@ -46,6 +48,12 @@ $module_context->mock(
   },
 );
 
+$module_languages->mock(
+    _get_language_dirs => sub {
+        return @languages
+    }
+);
+
 delete $ENV{HTTP_ACCEPT_LANGUAGE};
 
 my $query = CGI->new();
@@ -59,3 +67,24 @@ is(C4::Languages::getlanguage($query), 'en', 'default to English if no language
 Koha::Cache::Memory::Lite->get_instance()->clear_from_cache('getlanguage');
 $return_undef = 1;
 is(C4::Languages::getlanguage($query), 'en', 'default to English if no database');
+
+subtest 'when interface is not intranet or opac' => sub {
+    plan tests => 3;
+
+    my $cache = Koha::Cache::Memory::Lite->get_instance;
+    C4::Context->interface('api');
+
+    @languages = ('fr-FR', 'de-DE', 'en');
+
+    $ENV{HTTP_ACCEPT_LANGUAGE} = 'de-DE';
+    $cache->clear_from_cache('getlanguage');
+    is(C4::Languages::getlanguage(), 'de-DE', 'Accept-Language HTTP header is respected');
+
+    Koha::Language->set_requested_language('fr-FR');
+    $cache->clear_from_cache('getlanguage');
+    is(C4::Languages::getlanguage(), 'fr-FR', 'but language requested through Koha::Language is prefered');
+
+    @languages = ();
+    $cache->clear_from_cache('getlanguage');
+    is(C4::Languages::getlanguage(), 'en', 'fallback to english when no language is available');
+};
diff --git a/t/db_dependent/api/v1/items.t b/t/db_dependent/api/v1/items.t
index 2d5592d091..4dfcc2200c 100755
--- a/t/db_dependent/api/v1/items.t
+++ b/t/db_dependent/api/v1/items.t
@@ -32,6 +32,7 @@ use Mojo::JSON qw(encode_json);
 use C4::Auth;
 use Koha::Items;
 use Koha::Database;
+use Koha::Language;
 
 my $schema  = Koha::Database->new->schema;
 my $builder = t::lib::TestBuilder->new;
@@ -256,7 +257,7 @@ subtest 'list_public() tests' => sub {
 
 subtest 'get() tests' => sub {
 
-    plan tests => 34;
+    plan tests => 37;
 
     $schema->storage->txn_begin;
 
@@ -346,6 +347,13 @@ subtest 'get() tests' => sub {
       ->json_is( '/not_for_loan_status' => 0, 'not_for_loan_status is 0' )
       ->json_is( '/effective_not_for_loan_status' => 3, 'effective_not_for_loan_status now picks up itemtype level - item-level_itypes:0' );
 
+    my $module = Test::MockModule->new('C4::Languages');
+    $module->mock( _get_language_dirs => sub { return 'en', 'de-DE' } );
+    $schema->resultset('Localization')->create({ entity => 'itemtypes', code => $itype->itemtype, lang => 'de-DE', translation => 'translated' });
+    $t->get_ok( "//$userid:$password@/api/v1/items/" . $item->itemnumber, { 'X-Koha-Embed' => '+strings', Cookie => 'KohaOpacLanguage=de-DE', 'Accept-Language' => 'en' } )
+      ->status_is( 200, 'SWAGGER3.2.2' )
+      ->json_is( '/_strings/item_type_id/str' => 'translated', 'translations in _strings use language set in KohaOpacLanguage cookie' );
+
     $schema->storage->txn_rollback;
 };