Gustav Wilhelm Ludwig Struve (November 1, 1858 – November 4, 1920) was a Russian astronomer, part of the famous Baltic German Struve family. In Russian, his name is sometimes given as Lyudvig Ottovich Struve (Людвиг Оттович Струве) or Lyudvig Ottonovich Struve (Людвиг Оттонович Струве).
Gustav Wilhelm Ludwig Struve was born in 1858 in Tsarskoye Selo – a former Russian residence of the imperial family and visiting nobility, located 26 kilometers (16 mi) south from the center of St. Petersburg. He was the fourth son of Otto Wilhelm von Struve and Emilie Dyrssen (1823–1868) and a younger brother of astronomer Hermann Struve. Gustav followed his family traditions and between 1876 and 1880 studied astronomy at the University of Tartu. For his post-graduate research started at the Pulkovo Observatory which was headed by his father. In 1883, Gustav defended his PhD thesis on "Resultate aus den in Pulkowa angestellen Vergleichungen von Procyon mit benachbarten Sternen" (Results obtained in Pulkovo on relation of Procyon with the neighboring stars). Between 1883 and 1886, Struve was staying abroad in several European observatories, including those in Bonn, Milan, Paris and Leipzig. His major influences in astronomy were his father and the Italian astronomer Giovanni Schiaparelli. Between 1886 and 1894, Struve worked as an astronomer at the Tartu Observatory. In 1887, using results obtained during his European trip, he prepared and defended the habilitation thesis titled "Neue Bestimmung der Constante der Precession und der eigenen Bewegung des Sonnensystems" (New determination of the constant of precession and of the motion of the Solar System).