Brevetoxin B was isolated from the red tide organism Karenia brevis in 1981 as the first example of marine polycyclic ethers. This compound shows potent neurotoxicity, by binding to sodium channels, causing massive fish kills and human health problems. Since further biological studies are hampered by the limited availability from nature, chemical synthesis has been the sole realistic way to obtain sufficient amounts of brevetoxin B. Moreover, the huge molecular architecture is a particularly attractive target for synthetic chemists. In this account, we describe the highly convergent total synthesis of brevetoxin B based on our methodology, including intramolecular allylation and subsequent ring-closing metathesis.