[2] Olympiacos is parent to a number of different competitive departments which participate in football, basketball, volleyball, water polo, handball, athletics, swimming, table tennis and boxing amongst many others—and have won numerous European and domestic titles over the club's history.

Olympiacos' athletes have become Olympic medal winners, as well as World and European champions, while they are integral part of the Greek national teams.

The club maintains Academies with state of the art training facilities, where thousands of children have the opportunity to learn about sports and practice.

Olympiacos CFP have granted Greek sports and the club itself numerous Olympic, Worldwide and European honours.

[60] Olympiacos CFP was the first Greek club that made it possible for its fans to become members, and granted them the right of voting for the board of directors.

Notis Kamperos, a senior officer of the Hellenic Air Force, proposed the name Olympiacos and the profile of a laurel-crowned Olympic winner as the emblem of the new club.

Michalis Manouskos, a prominent Piraeus industrialist, expanded the name to its complete and current status, Olympiacos Syndesmos Filathlon Pireos, a name that symbolizes and encompasses the morality, the honour, the vying, the splendor, the sportsmanship and the fair play value of the Olympic ideal of Ancient Greece, which was totally consistent with the club's emblem.

[62] Besides Kamperos and Manouskos, among the most notable founding members were Stavros Maragoudakis, the Post Office director, Nikos Andronikos, a merchant, Dimitrios Sklias, a Hellenic Army officer, Nikolaos Zacharias, an attorney, Athanasios Mermigas, a notary public, Kostas Klidouchakis, who became the first goalkeeper in the club's history, Ioannis Kekkes, a stockbroker, and above all, the Andrianopoulos family.

The five brothers, Yiannis, Giorgos, Dinos, Vassilis and Leonidas Andrianopoulos raised the reputation of the club and brought it to its current glory.

[71] Olympiacos is the most successful Greek football club in European competitions, being the only club from Greece to have won a major European trophy; they won the UEFA Europa Conference League in 2023–24, sealing their title by winning against Italian side Fiorentina 1–0 in the Final.

In 2013, Olympiacos won their third EuroLeague title and became the only Greek club and only the third club in European basketball history to be crowned back-to-back European champions in the modern EuroLeague Final Four era, after beating Real Madrid 100–88 in the London final.

In 2023, they won the CEV Challenge Cup, beating rivals Panathinaikos in the semi-finals and Maccabi Tel Aviv in the final.

Olympiacos men's water polo team is one of the most successful teams in Europe and a traditional powerhouse of continental water polo,[86][87] having won 2 LEN Champions Leagues (2001–02, 2017–18),[88][89] 1 LEN Super Cup (2002) and 2 Triple Crowns (2002, 2018), the only Greek club to have been crowned European Champions.

After the 2014–15 LEN Euro League win of the women's department, parent club Olympiacos CFP became the second sports club in continental water polo history to have been crowned European Champions with both its men's and women's teams and the only one in Europe with both these departments currently active.

[100] Olympiacos lifted the LEN Euro League title undefeated and having won 8 straight matches without even a single draw.

In 2021 Olympiacos won their second LEN Euro League title in Budapest, beating home teams UVSE (9–8 in the semi-final) and Dunaújvárosi (7–6 in the final) with a roster composed entirely of Greek players.

In 2022 Olympiacos were crowned back-to-back European Champions in Piraeus, beating UVSE (18–11 in the semi-final) and Sabadell (11–7 in the final).

The season 2017–18 was the most successful in the club's history and the most successful by any Greek women's volleyball club in history; besides winning the aforementioned CEV Challenge Cup in their second final presence in a row, they won the domestic competitions undefeated, with 25–0 wins in the League, finishing the season with only two sets lost in an unprecedented 75–2 set record, and 4–0 wins in the Cup with a 12–1 set record, achieving a Continental Treble and their sixth consecutive domestic Double.

[122] They also won the Greek Cup, beating PAOK in the semi-final and ASE Douka in the final to complete the domestic Double.

Olympiakos swimming department holds the world record of having won at least one title in every season, for fifty-four (54) consecutive years.

Olympiacos has produced some of the greatest swimmers in Greek swimming history, such as the Olympic silver medalist, five-time Olympian, two-time World Champion, World Cup gold medalist, and two-time European Champion[125] Spyros Gianniotis, who is considered the greatest Greek swimmer of all time.

The department has had in its ranks some of the greatest Greek athletes ever in the track and field events including Olympic medalists, as well as World, European, Mediterranean, Balkan and Panhellenic Champions.

Cases in point are: Konstantinos Kenteris, Fani Halkia, Ekaterini Thanou, Mirela Maniani, Niki Bakoyianni, Hrysopiyi Devetzi, Niki Xanthou, Dimitrios Chondrokoukis, Labros Papakostas, Periklis Iakovakis, Ekaterini Voggoli, Hristos Meletoglou, Stelios Dimotsios, Dimitrios Polymerou, Haralabos Papadias, Maria Karastamati, Flora Redoumi, Athina Papayianni, Spyridon Vasdekis, Aggeliki Tsiolakoudi, Louis Tsatoumas and Emmanouil Karalis.

The most important athletes in the history of the department were the Koutsioumpas brothers, the Athens' Olympic Bronze Medalist Artiom Kiouregkian and Christos Gikas amongst many others.

The service is attended by thousands of fans every year, who are rhythmically shouting the phrase "Αδέλφια, ζείτε, εσείς μας οδηγείτε."