diff --git a/src/NodaWikidataFetcher.php b/src/NodaWikidataFetcher.php
index 85cce49..d284bb2 100644
--- a/src/NodaWikidataFetcher.php
+++ b/src/NodaWikidataFetcher.php
@@ -12,6 +12,11 @@ declare(strict_types = 1);
  */
 final class NodaWikidataFetcher {
 
+    const WIKIDATA_FETCH_HEADERS = [
+        'User-Agent: museum-digital-bot GND-to-Wikidata PHP/' . PHP_VERSION,
+        'Accept: application/sparql-results+json',
+    ];
+
     const LANGUAGES_MAIN_DESC = ['de', 'da', 'en', 'es', 'fr', 'hu', 'it', 'jp', 'nl', 'pt', 'ru', 'sv', 'zh'];
     const LANGUAGES_TO_CHECK = ['ar', 'bn', 'cs', 'da', 'de', 'el', 'en', 'es', 'fa', 'fi', 'fr', 'ha', 'he', 'hi', 'hu', 'id', 'it', 'ja', 'ka', 'ko', 'nl', 'pl', 'pt', 'ro', 'ru', 'sv', 'sw', 'ta', 'th', 'tl', 'tr', 'ur', 'vi', 'zh'];
 
@@ -176,6 +181,96 @@ final class NodaWikidataFetcher {
 
     }
 
+    /**
+     * Runs a SPARQL query against the Wikidata SPARQL endpoint.
+     *
+     * @param string $sparqlQuery Query string.
+     *
+     * @return array<mixed>
+     */
+    public static function sparqlQuery(string $sparqlQuery):array {
+
+        $url = 'https://query.wikidata.org/sparql?query=' . urlencode($sparqlQuery);
+        $result = MD_STD::runCurl($url, 10000, self::WIKIDATA_FETCH_HEADERS);
+
+        return json_decode($result, true);
+
+    }
+
+    /**
+     * Formulates a SPARQL query string for fetching from Wikidata based on an external ID.
+     *
+     * @param string $repoName   Name of the repository.
+     * @param string $externalId ID in the external repository.
+     * @param string $repoPId    Optional P-ID of the external repository. Needed for
+     *                           Geonames and TGN, obsolete otherwise.
+     *
+     * @return string
+     */
+    public static function formulateWikidataQueryByExtId(string $repoName, string $externalId, string $repoPId = ''):string {
+
+        if (empty($repoPId)) {
+
+            if (empty(NodaWikidataFetcher::P_IDS_NODA_TAGS[$repoName])) {
+                throw new MDmainEntityNotExistentException("Unknown external repository. The following repositories are known with their Wikidata ID: " . implode(', ', array_keys(NodaWikidataFetcher::P_IDS_NODA_TAGS)));
+            }
+
+            $repoPId = NodaWikidataFetcher::P_IDS_NODA_TAGS[$repoName];
+
+        }
+
+        $sparqlQueryString = 'SELECT ?id ?idLabel WHERE {
+            ?id wdt:' . $repoPId . ' "' . $externalId . '".
+            SERVICE wikibase:label {
+                bd:serviceParam wikibase:language "en" .
+            }
+        }';
+
+        return $sparqlQueryString;
+
+    }
+
+    /**
+     * Gets the Wikidata ID based on a result from Wikidata's SPARQL endpoint.
+     *
+     * @param array<mixed> $queryResult Query result.
+     *
+     * @return string
+     */
+    public static function readWikidataIdFromSparqlResult(array $queryResult):string {
+
+        if (count($queryResult['results']['bindings']) !== 1) return '';
+
+        if (!empty($wikidataLink = $queryResult['results']['bindings'][0]['id']['value'])) {
+            if (($endSlashPos = strrpos($wikidataLink, '/')) !== false) {
+                return substr($wikidataLink, $endSlashPos + 1);
+            }
+        }
+
+        return '';
+
+    }
+
+    /**
+     * Queries Wikidata by an external repository's ID and returns the matching Q-ID
+     * if there is any.
+     *
+     * @param string $repoName   Name of the repository.
+     * @param string $externalId ID in the external repository.
+     * @param string $repoPId    Optional P-ID of the external repository. Needed for
+     *                           Geonames and TGN, obsolete otherwise.
+     *
+     * @return string
+     */
+    public static function getWikidataIdByExternalId(string $repoName, string $externalId, string $repoPId = ''):string {
+
+        $sparqlQueryString = self::formulateWikidataQueryByExtId($repoName, $externalId, $repoPId = '');
+
+        $queryResult = self::sparqlQuery($sparqlQueryString);
+        return self::readWikidataIdFromSparqlResult($queryResult);
+
+    }
+
     /**
      * Gets translation source Wikipedia pages from Wikidata.
      *