Johannes Bernhard Graf von Welczeck (2 September 1878 – 11 October 1972) was a German diplomat who served as the last German ambassador to France before World War II.

Aristocrat Welczeck was born into an aristocratic family in Laband (modern Łabędy, Poland) in the Upper Silesia province of the Kingdom of Prussia, his parents being Count Bernhard von Welczeck (1844–1917) and Countess Louise von Hatzfeldt zu Trachenberg (1852–1909). Welczeck studied at the University of Bonn in Bonn and in 1897 joined the exclusive Corps Borussia Bonn student club, which was reserved for royalty and nobility at the time.

Diplomat In 1904, he joined the highly elitist Auswärtiges Amt (Foreign Office), one of the most prestigious branches of the state under the German Empire. Welczeck began his career as the German consul-general in New Delhi. In 1908, he became the first secretary to Hans von und zu Bodman, the German ambassador to Chile. On 20 November 1910, he married Luisa Balmaceda y Fontecilla (1886–1973) in Santiago, by whom he had four children. Welczeck's wife was a member of the powerful Balmaceda family, one of the richest and most influential families in Chile. Most of his duties in Chile concerned lobbying for arms contracts for German firms, most notably the firm of Krupp AG, the largest corporation in Europe and one of the world's biggest manufacturers of weapons. The Chilean Army had been trained by a German military mission, and German influence was strong in Chile. In 1915, he became the Prussian chargé d'affairs in Dresden, Saxony. In January 1917, upon the death of his father, he inherited the title of count, and was henceforward known as Count von Welczeck.

From 1923 to 1925, he was the German minister in Budapest. From 1925 to 1936, he was the German ambassador in Madrid. In January 1926 he was involved in efforts to circumvent the disarmament clauses of the Treaty of Versailles by having the Deutsche Bank make a five million reichsmark loan via the Banco Alemán Transatlantico (which it owned) to the Spanish industrialist Horacio Echevarrieta, in exchange for which Echevarrieta opened up a torpedo factory for the Reichsmarine in Bilbao.

From 9 May 1932 to 15 July 1932, he headed the German delegation at the World Disarmament Conference in Geneva. As someone from Upper Silesia, which had been violently partitioned between Germany and Poland in 1921, Welczeck was well known for his ferocious hatred of Poles, and spent much of his time in Geneva clashing with the Polish foreign minister, August Zaleski, who headed the Polish delegation. The American historian Carole Fink described Welczeck as a "notorious Polonophobe" whose constant Polish-bashing did much to annoy the other delegates at the League of Nations. When the Sanation regime introduced a land reform law in the Polish Corridor to seize the land holdings of the Junker estates, Welczeck represented Germany at the League of Nations Human Rights Committee, where he argued that the land reform in the Polish Corridor was targeting farms owned by Germans to "Polonise" the Corridor, thereby violating the Minorities Treaty, leading to a notable clash with Zaleski. Fink noted that through Welczeck had a strong case in that the land reform had largely exempted the estates owned by the szlachta, he weakened it by his strident and shill manner while Zaleski made a better impression by being calm and conciliatory.

In August 1933, Welczeck returned to Germany for his first meeting with Adolf Hitler, where he spoke at much length about the "Bolshevik danger" in Spain. Welczeck portrayed Spain on the brink of a Communist revolution, describing Spain as a nation hard hit by the Great Depression where many of the unemployed were joining the Spanish Communist Party. Welczeck wanted German intelligence to play a greater role in Spain. Welczeck stated that Hitler met his plan "only half-way", agreeing to send Abwehr agents disguised as businessmen to Spain to monitor Spanish Communists and anarchists, but vetoed his plans for intelligence-sharing with the Spanish police. On 1 October 1934, Welczeck joined the Nazi Party. In 1934–35, Welczeck was highly alarmed by social unrest in Spain and favored having General Francisco Franco appointed minister of war. Welczeck was obsessive in his fears of Communism in Spain, constantly warning Berlin that a revolution could take place at any moment and that all of the property and assets owned by German businesses in Spain would be lost.

Ambassador in Paris The Front populaire era and the Spanish Civil War In April 1936, Welczeck arrived in Paris as the new German ambassador. The French historian Lucas Delattre described Welczeck as a "diplomat of the old school", being well known in Paris for his courtly, suave manners (albeit with an irascible streak); elegant clothing; and his fluent French, which he spoke with a strong upper-class accent. Welczeck had familial connections with the French aristocracy via his step-aunt, the Comtesse Jean de Castelane. Welczeck was the only German ambassador in Paris during the interwar era to be admitted to the Union, one of the most exclusive social clubs in Paris that only accepted the creme-de-creme of the French elite. However, Welczeck was not favored with close friendships with the French cabinet ministers in the same way that his Anglo-American counterparts, namely Sir Eric Phipps and William Christian Bullitt Jr. were. Both Bullitt and Phipps were more popular socially with the French elite than Welczeck, who was somewhat disliked on the account of the regime he loyally served. Hitler's tendency to recall Welczeck back to Germany during moments of crisis as he did in September 1938, March–April 1939 and August 1939 limited his effectiveness as an ambassador with Baron Ernst von Weizsäcker, the State Secretary of the Auswärtiges Amt, complaining that when Germany needed Welczeck the most in Paris he was absent.

Shortly after he arrived in Paris, the Front populaire won the French National Assembly election of 3 May 1936, leading to a coalition government headed by the Socialist leader Leon Blum coming to power. Through Blum was a Socialist and a Jew, Welczeck's relations with him were cordial enough. Blum found Welczeck together with the Reichsbank president Hjalmar Schacht to be the more reasonable sort of Nazis, stating he considered both Welczeck and Schacht to be "rational, civilized Europeans" whom it was possible for him to negotiate with. Notably, Hitler refused to meet Blum under any conditions, and as such Welczeck became Blum's main conduit with the German government. Blum and his cabinet made a point of visiting Welczeck at the German embassy to tell him that France wanted good relations with Germany and hoped for a return to the Locarno era.

As the former ambassador to Spain, Welczeck played a major role as an adviser on Spanish affairs following the appeal for aid from the Spanish Nationalists in July 1936. Right from the start, Welczeck favored aid to Franco over General Emilio Mola, the other leader of the junta that had launched the botched coup d'état of 17 July 1936 that caused the civil war. He was opposed to two messengers from Mola in Paris going on to Berlin in order to favor Franco, successfully arguing for the Reich to deny permission for Mola's representatives to enter Berlin. Welczeck initially advocated caution in Spain, believing that the junta of rebellious generals who just failed to overthrow the Second Spanish Republic would lose the civil war. More importantly, the new Popular Front government in Paris led by Premier Leon Blum had decided to aid the Spanish Republicans with military aid, which led him to fear that the civil war in Spain could cause a Franco-German war "prematurely" before German rearmament was completed. The news that Hitler had decided on 24 July 1936 to intervene in Spain caused him much worry. The fact that the Blum government under strong pressure from Britain agreed to a policy of non-intervention in Spain was a source of much relief for Welczeck, who became more supportive of German intervention in Spain once it was clear that there was no danger of French intervention. However, even after the intervention occurred he cabled Berlin urging the government to limit the scale of the intervention and warning that the German Condor Legion air raids on Spain were causing the French Left to become more supportive of further intervention on behalf of the Republicans.

In October 1936 in a meeting at the Reich Chancellery, Hitler told the French ambassador in Berlin, André François-Poncet, that France was on the brink of civil war and that : "If Communism triumphed in France, it would be impossible for him, Hitler, to consider this event an internal French affair". The next day, the French Foreign Minister Yvon Delbos handed Welczeck a note formally protesting against Hitler's statement, stating it was unacceptable for Hitler to make statements implying a right to intervene in French domestic affairs. Welczeck defended Hitler, claiming despite what he had said to François-Poncet that Hitler was only engaging in "defensive measures" such as building the Siegfried Line in the newly remilitized Rhineland as he blamed the problems in Franco-German relations entirely on the French. The meeting ended on an extremely unfriendly tone with Welczeck and Delbos arguing about what Hitler had said and meant. In November 1936, Welczeck reported to Berlin that the Spanish Civil War had led to: "the downright hysterical nervousness that has been evident among the public here for several days and has started crack-brained rumours circulating regarding the inevitability of war, simultaneous military attacks on France from the east and south planned by Germany".

In December 1936, Delbos contracted Welczeck with an offer to mediate an end to the Spanish Civil War. Provided that the civil war in Spain could be ended via Franco-German mediation, Delbos was willing to discuss the return of the former German colonies in Africa held by France as League of Nations mandates, an end to the arms race, and an economic agreement to lower tariffs in order to end the trade wars in Europe. The introduction of the Four Year Plan in Germany in September 1936 had caused much alarm in France. This was especially the case as the Four Year Plan envisioned Germany becoming self-sufficient by developing substitutes for commonalties such as oil, even through it was likely to cost hundreds of millions of Reichsmarks. In the 1930s, 80% of the oil Germany used was imported from the United States, Venezuela, and Mexico and Hitler's claim that Germany needed to be self-sufficient in artificial oil because of the alleged danger of the Soviet Navy seizing control of the North Atlantic was not widely believed in Paris. Within the French government, the implications of the Four Year Plan with its call for Germany to have a wartime economy by 1940 were well understood.