《機動戰士鋼彈F91》是於1991年上映的日本動畫電影，由富野由悠季執導、SUNRISE製作，屬於鋼彈系列的正統劇場版作品。故事的時間軸設定在《機動戰士鋼彈 逆襲的夏亞》之後三十年，宇宙世紀0123年。當時人類社會表面上度過一段短暫的和平，但在宇宙殖民地內，貴族主義逐漸抬頭，並以羅納家族為首組成武裝組織「骷髏尖兵」（又稱骨十字先鋒軍），企圖建立全新的「宇宙巴比倫」國度，以統治殖民地居民。

劇情以年輕的學院學生西布克·阿諾為主角展開。他原本只是一名普通殖民地青年，卻在「邊境IV」遭到骷髏尖兵的猛烈襲擊後，被迫踏入戰火之中。為了生存，他與妹妹莉絲及朋友們一同逃難，最終登上地球聯邦軍的練習艦「太空方舟」，並在情勢所逼下駕駛起仍在整備中的新型機動戰士——鋼彈F91。隨著戰鬥展開，西布克在戰場上與戀人賽西莉重逢，但她的真實身份卻是羅納家族的後裔，被迫成為宇宙巴比倫建國的象徵。兩人被命運推向敵對的立場，但最終賽西莉選擇站到西布克一方，共同對抗骷髏尖兵的領袖「鐵假面」，並終於在激戰中擊敗對手。整個故事以青年們的掙扎、對戰火的恐懼，以及在愛情與宿命間的抉擇為主軸，帶有濃厚的悲劇與希望交織的色彩。

製作上，《鋼彈F91》原本計劃為52集的長篇電視動畫系列，但由於製作衝突與資源調整，最終被壓縮為一部115分鐘的劇場版電影。這也造成劇情節奏過於緊湊，許多世界觀與人物設定未能充分展開。儘管如此，本作仍展示安彥良和的人物設計與大河原邦男的機械設計，特別是鋼彈F91本身小型化卻性能強大的設定，為系列帶來全新的技術想像。

至於市場評價方面，影片上映後票房表現並不理想，未達到製作方的期待，也直接導致後續電視版企劃被取消。批評的聲音主要集中在劇情壓縮過度，角色關係和戰爭背景缺乏足夠鋪陳，使得觀眾難以完全投入。然而，角色的塑造與美術設計卻普遍受到肯定，特別是西布克與賽西莉之間跨越立場的愛情故事，給人留下深刻印象。隨著時間推移，本作逐漸被系列愛好者以不同的角度重新審視，雖然未能成為票房成功的作品，但在鋼彈系列的整體歷史中，它代表一個從「逆襲的夏亞」過渡到新世代鋼彈作品的關鍵橋樑。

長遠來看，《鋼彈F91》雖然未能展開完整的「宇宙巴比倫建國戰爭」篇章，但後續的漫畫《機動戰士海盜鋼彈》以回憶與補充的方式延續了這條故事線，使得《F91》成為後續宇宙世紀作品的重要前奏。對鐵杆粉絲而言，它是一部雖有缺憾卻不可或缺的鋼彈劇場版，其實驗性質與未盡的野心，也讓它在鋼彈系列中佔據獨特的位置。

Mobile Suit Gundam F91 is a Japanese animated film released in 1991, directed by Yoshiyuki Tomino and produced by Sunrise. It is considered a canonical theatrical entry in the Gundam franchise. The story takes place in U.C. 0123, thirty years after Mobile Suit Gundam: Char’s Counterattack. Although humanity appeared to enjoy a brief period of peace, aristocratic ideals began to resurface within the space colonies. Led by the influential Ronah family, an armed organization known as the “Crossbone Vanguard” (also called the “Skull Soldiers”) was formed, aiming to establish a new nation called “Cosmo Babylonia” to dominate the colonists.

The narrative follows Seabook Arno, a young academy student who becomes the reluctant protagonist. Originally just an ordinary colonial youth, Seabook is thrust into the chaos of war when the Crossbone Vanguard launches a sudden and devastating assault on Frontier IV. Forced to flee with his younger sister Rees and friends, Seabook eventually boards the Earth Federation’s training vessel Space Ark. Under desperate circumstances, he takes control of the newly developed but unfinished mobile suit—Gundam F91. As the conflict escalates, he is reunited on the battlefield with his lover Cecily, only to discover that she is in fact a descendant of the Ronah family and has been positioned as the symbolic figure of Cosmo Babylonia. Though fate pushes them into opposing roles, Cecily ultimately chooses to fight alongside Seabook. Together, they confront the Crossbone Vanguard’s leader, Iron Mask, and succeed in defeating him after an intense battle. The story emphasizes the struggles of youth, the terror of war, and the painful choices between love and destiny, blending tragedy with hope.

In terms of production, Gundam F91 was initially planned as a 52-episode television series. However, due to internal conflicts and resource issues, the project was condensed into a 115-minute feature film. This resulted in a narrative that felt overly compressed, leaving much of the world-building and character development underexplored. Nonetheless, the film showcased Yoshikazu Yasuhiko’s character designs and Kunio Okawara’s mechanical designs, with the Gundam F91 itself standing out for its smaller frame paired with formidable performance—a fresh technological concept for the series.

Reception-wise, the film underperformed at the box office and failed to meet commercial expectations, which in turn led to the cancellation of its planned TV series continuation. Criticism centered on the rushed pacing, lack of depth in the characters’ relationships, and insufficient exploration of the larger political conflict, making it difficult for viewers to fully immerse themselves. However, the character portrayals and visual design were generally praised, especially the love story between Seabook and Cecily, which left a lasting impression. Over time, fans have come to reevaluate the film more favorably, viewing it as an ambitious if flawed attempt that served as a crucial bridge between Char’s Counterattack and the next generation of Gundam works.

In the long run, although Gundam F91 did not deliver the complete narrative of the “Cosmo Babylonia War” as originally intended, its story was partially continued in manga form through Mobile Suit Crossbone Gundam, which expanded upon the aftermath. For dedicated fans, F91 remains an essential though imperfect theatrical entry—an experimental work with unfulfilled ambitions that nonetheless carved out a unique place within the Gundam legacy.