Abbe, Cleveland (1838–1916)

Abbe, Ernst (1840–1905)

Abd-er-Rahmān ibn-Umar (Abd-er-Rahmān ibn-Umar)

Abel, Frederick Augustus (1827–1902)

Abel, John Jacob (1857–1938)

Abel, Neils Henrik (1802–1829)

Abercrombie, John (1726–1806)

Abernethy, John (1764–1831)

Abetti, Giorgio (1882–1982)

Abler, Ronald (Francis) (1939– )

Abraham, Edward Penley (1913–1999)

Abrikosov, Alexei Alexeyevich (1928–2017)

Abulcasis (936–1013)

Accum, Friedrich Christian (1769–1838)

Achard, Franz Karl (1753–1821)

Acheson, Edward (Goodrich) (1856–1931)

Achillini, Alessandro (1463–1512)

Actuarius, Johannes (died 1283)

Adams, John Couch (1819–1892)

Adams, Leason Heberling (1887–1969)

Adams, Roger (1889–1971)

Adams, Walter Sydney (1876–1956)

Adanson, Michel (1727–1806)

Addison, Thomas (1793–1860)

Ader, Clément (1841–1926)

Adleman, Leonard (1945– )

Adler, Alfred (1870–1937)

Adler, Stephen L(ouis) (1939– )

Adrian, Edgar Douglas (1889–1977)

Agassiz, (Jean) Louis Rodolphe (1807–1873)

Agassiz, Alexander (Emmanuel Rodolphe) (1835–1910)

Agnesi, Maria Gaetana (1718–1799)

Agre, Peter (1949– )

Agricola, Georgius (1490–1555)

Aiken, Howard Hathaway (1900–1973)

Airy, George Biddell (1801–1892)

Aitken, Robert Grant (1864–1951)

Akasaki, Isamu (1929– )

Akeley, Carl (Ethan) (1864–1926)

Al-Battani, abu-Abdullah Muhammad ibn-Jabir (c. 850–c. 929)

al-Farghānī, abu-al-Abbās Ahmad (lived 9th century AD)

al-Sufi (903–986)

Albee, Fred (Houdlette) (1876–1945)

Albert, Abraham Adrian (1905–1972)

Albone, Dan (1860–1906)

Albright, Horace Marden (1890–1987)

Alder, Kurt (1902–1958)

Aldrin, Buzz (1930– )

Aldrovandi, Ulisse (1522–1605)

Aleksandrov, Pavel Sergeevich (1896–1982)

Alexander, Frederick Matthias (1869–1955)

Alexander, Hattie Elizabeth (1901–1968)

Alexanderson, Ernst Frederik Werner (1878–1957)

Alferov, Zhores Ivanovich (1930– )

Alford, Andrew (1904–1992)

Alfvén, Hannes Olof Gösta (1908–1995)

Alhazen, Abu Alī al-Hassan ibn al-Haytham (c. 965–1038)

Allard, Harry A(rdell) (1880–1963)

Allbutt, Thomas Clifford (1836–1925)

Allen, Clarence Roderic (1925– )

Allen, Paul Gardner (1953– )

Allison, James Patrick (1948– )

Allport, Gordon (Willard) (1897–1967)

Alpher, Ralph Asher (1921–2007)

Alpini, Prospero (1553–1616)

Alter, David (1807–1881)

Altman, Sidney (1939– )

Alvarez, Luis Walter (1911–1988)

Alzheimer, Alois (1864–1915)

Amano, Hiroshi (1960– )

Ambartsumian, Viktor Amazasp Amazaspovich (1908–1996)

Amdahl, Gene (1922–2015)

Ames, Adelbert (1880–1955)

Ames, Oakes (1874–1950)

Amici, Giovanni Battista (1786–1863)

Amman, Johann Konrad (1663–1730)

Ampère, André-Marie (1775–1836)

Amsler-Laffon, Jakob (1823–1912)

Anastasi, Anne (1908–2001)

Anaximander the Elder (c. 610–546 BC)

Andersen, Dorothy H(ansine) (1901–1963)

Anderson, Carl David (1905–1991)

Anderson, Don Lynn (1933– )

Anderson, Edgar S(hannon) (1897–1969)

Anderson, John R.

Anderson, Philip Warren (1923– )

Andreessen, Marc (1971– )

Andrews, Roy Chapman (1884–1960)

Andrews, Thomas (1813–1885)

Anfinsen, Christian Boehmer (1916–1995)

Angell, James (Rowland) (1869–1949)

Ångström, Anders Jonas (1814–1874)

Anning, Mary (1799–1847)

Anokhin, Piotre Kuzmich (1897–1974)

Anthes, Richard (Allen) (1944– )

Antoniadi, Eugène Marie (1870–1944)

Antyllus (lived c. AD 150)

Apgar, Virginia (1909–1974)

Apianus, Petrus (1495–1552)

Apollonius of Perga (c. 245–c.190 BC)

Appert, Nicolas François (c.1750–1841)

Appleton, Edward Victor (1892–1965)

Arago, (Dominique) François (Jean) (1786–1853)

Arber, Agnes (1879–1960)

Arber, Werner (1929– )

Archigenes of Apamea (born c. 54)

Archimedes (c. 287–212 BC)

Aretaeus of Cappadocia (lived 2nd century AD)

Argand, Jean Robert (1768–1822)

Argelander, Friedrich Wilhelm August (1799–1875)

Argyris, Chris(topher) (1923–2013)

Aristarchus of Samos (c. 320–c. 250 BC)

Aristotle (384–322 BC)

Arkell, William Joscelyn (1904–1958)

Arkwright, Richard (1732–1792)

Armelagos, George J(ohn) (1936–2014)

Armstrong, Edwin Howard (1890–1954)

Armstrong, Neil Alden (1930–2012)

Armstrong, William George (1810–1900)

Arnold, Frances Hamilton (1956– )

Arnold, John (1736–1799)

Arnon, Daniel I(srael) (1910–1994)

Arp, Halton Christian (1927–2013)

Arrhenius, Svante August (1859–1927)

Artedi, Peter (1705–1735)

Artin, Emil (1898–1962)

Aselli, Gasparo (1581–1626)

Ashburner, Michael (1942– )

Ashford, Bailey Kelly (1873–1934)

Ashkin, Arthur (1922– )

Aspdin, Joseph (1779–1855)

Aston, Francis William (1877–1945)

Atanasoff, John Vincent (1903–1995)

Atkins, Robert (1930–2003)

Atkinson, Richard (1920–1994)

Atkinson, Robert D'escourt (1898–1982)

Attenborough, David Frederick (1926– )

Atwater, Brian F.

Atwood, George (1745–1807)

Audubon, John James Laforest (1785–1851)

Auer, Carl (Auer, Carl)

Austin, Herbert (1866–1941)

Austin, Mary (1868–1934)

Autolycus (astronomy) (lived 4th century BC)

Auzout, Adrien (1622–1691)

Avenzoar (1091–1161)

Avery, Oswald Theodore (1877–1955)

Avicenna (980–1037)

Avogadro, Amedeo (1776–1856)

Avram, Henrietta D (Davidson) (1919–2006)

Axel, Richard (1946– )

Axelrod, Julius (1912–2004)

Ayala, Francisco J(osé) (1934– )

Ayrton, Hertha (Phoebe Sarah) Marks (1854–1923)

Ayrton, William Edward (1847–1908)