Generally preceded by the definite article the, the offensive phrase yellow peril denotes the political, military or economic threat regarded as being posed by certain peoples of South-East and East Asia, especially the Chinese and the Japanese.

In this phrase, with reference to the pigmentation of the skin, the adjective yellow is offensively applied to persons of South-East or East Asian ethnic origin.

The phrase yellow peril occurs, for example, in Beyond fairy tale history: The untold story of anti-Chinese racism in America, by Jonathan P. Baird, published in the Concord Monitor (Concord, New Hampshire, USA) of Monday 24^th January 2022:

Into the 20^th century, the American tradition of welcoming immigrants was not extended to the Chinese. The ‘Yellow Peril’ racist ideology infected too many minds.

The phrase yellow peril is a loan translation from French péril jaune. One of the earliest occurrences of the French phrase péril jaune that I have found is from L’immigration chinoise en Australie [Chinese immigration in Australia], by the French politician Joseph Chailley (1854-1928), published in L’Économiste français (Paris, France) of Saturday 7^th July 1888:

La Chine a depuis quelques années pris l’habitude de parler ferme aux puissances européennes. Elle se sent forte de leurs divisions, elle a conscience de leurs ambitions et de leurs rivalités ; elle est pour eux le Péril Jaune, représenté aujourd’hui par l’invasion pacifique de ses nationaux, en attendant que ce soit, dans quelques siècles, par la puissance de ses armes.
     translation:
China has for a few years got into the habit of talking firmly to the European powers. She is feeling strong from their divisions, she is aware of their ambitions and of their rivalries; she is for them the Yellow Peril, represented today by the pacific invasion of her nationals, until it is, in a few centuries’ time, by the power of her weapons.

The earliest occurrences of the phrase yellow peril that I have found are as follows, in chronological order:

1-: From the South Wales Daily News (Cardiff, Glamorgan, Wales) of Saturday 12^th January 1895:

THE YELLOW PERIL.

The special correspondent of Le Soir, in a recent communication from St. Petersburg, says:—The Novosti, in spite of the denial by the Japanese, insists on the possibility of a future alliance between China and Japan against Europe. In effect, it says China and Japan (the latter possessing only an exterior varnish of civilisation, covering a barbarity and profound and fanatical hate against Europeans) offer in any union serious elements against European civilisation which will inevitably be annihilated if Europe does not take advantage of the opportunity and adopt measures in time to paralyse that immense danger by parcelling up China in place of leaving her to fuse with Japan.

2-: From The Standard (London, England) of Saturday 20^th April 1895:

(FROM OUR CORRESPONDENT.)

PARIS, Friday Night.
[…]
This evening’s Paris publishes a Note which is evidently inspired. After pointing out that China and Japan are now the subject of grave consideration in every Chancellerie in Europe, it remarks:—
“The Western Powers’ interest is to act in concert, not merely to secure the privileged position any of them may occupy in China, but to cope with the yellow peril (le péril jaune) which is now menacing Europe. The countries most directly concerned are France and Russia, on account of their possessions on the Chinese borders; England and Germany, in virtue of their commercial interests; and, finally, Spain in consequence of the proximity of the Philippine Islands. From the outset of hostilities, a special accord had been arrived at between the Cabinets of Paris, London, and St. Petersburg to preserve the most absolute neutrality both at Tokio [sic] and at Pekin. How far that accord may be affected by the conclusion of peace it would be premature to discuss, and as to the eventual attitude of Germany and Spain, we are as yet in the dark. So far as France is concerned, it is especially London that we have to look to.”

3-: From The Liverpool Echo (Liverpool, Lancashire, England) of Friday 26^th April 1895:

Paris, Friday.—The Matin to-day publishes an article by M. Francois de l’Oncle, entitled “The Yellow Peril,” and dealing with the danger to Europe involved in the peace treaty between Japan and China. In concluding the writer says: “Whatever may be the real intentions of England, they need not concern Russia, Germany, and France, if these Powers have really any programme to submit to the European concert. England alone is powerless, and is only formidable when she acts with other Powers. Let, therefore, the other Powers come to a definite understanding, and after an apparent resistance to their views England will join them.”

The earliest occurrence of the variant yellow menace that I have found is from the review of Concurrence et chômage: nos rivaux, nos charges, notre routine, by the French diplomat and politician Paul d’Estournelles de Constant (1852-1924), published in La Revue des Deux Mondes (Paris, France) of Thursday 15^th July 1897—review published in The Standard (London, England) of Friday 23^rd July 1897:

M. d’Estournelles is evidently familiar with all that has been put forward with regard to the danger of cheap Oriental labour—the Yellow Menace, as it is sometimes called.

In extended use, the phrase yellow peril is used of any of various yellow objects, substances, etc., regarded as a threat.

For example, the following is from Punch, or the London Charivari (London, England) of Wednesday 1^st November 1899:

A LONDON ANNUAL.

Sing a song of London fog,
Sulphurous and gritty;
Stealthily it comes to clog
Traffic in the City;
Do you live down Brixton way,
Or at Fulham, haply,
Travelling to Town each day?—
Shade of famous Tapley!
Even Mark might fume and fuss
At a “cruel crawling ’bus.

Sing a song of murky gloom,
Odorous and clinging;
(If the Influenza doom
Has not stopped your singing.)
For this “Yellow Peril” will,
Wheresoe’er you ’re dwelling,
Constitute a saffron ill
(Kindly note the spelling);
And the papers, I confess,
Nearly all seem “Yellow Press.”

Sing a song of sunless days,
When mine eyes alight on
Weather notes that speak the praise
Of beloved Brighton;
To my doctor I repair,
Visit voluntary;
Hope he ’ll think a change of air,
Highly necessary;
And will then prescribe for me,
Dose of—London-by-the-Sea.