Stock Market Open Today, August 18, 2026: Sensex, Nifty Decline After Lower Open As US-Iran Ceasefire Ends, Oil Tops $91

Mumbai, Aug 18: Indian benchmark indices opened weaker on Tuesday, extending Monday’s cautious tone as investors turned risk-averse after Iran threatened to shift to a “fully offensive” military posture in the Strait of Hormuz and the United States ruled out extending a temporary ceasefire agreement that expired on Monday.  

The BSE Sensex was trading at 77,432.83, down 295.33 points or 0.38%, while the NSE Nifty slipped to 24,223.75, down 63.90 points or 0.26%, as of 9:33 AM IST, building on the losses seen at Monday’s close when the Nifty had already fallen below the 24,300 mark. 

The renewed escalation in West Asia comes at a delicate moment for Indian equities, which were already grappling with weakness in IT stocks and persistent worries over elevated crude oil prices through last week and into Monday’s session.  

For Indian markets, the immediate transmission channel is crude oil. Brent crude, which had already surged to a peak of $126 a barrel during the conflict, roughly 75% above pre-war levels, settled more than $2 higher on Monday at $90.87 a barrel, and continued to firm up in early Tuesday trade. India imports the vast majority of its crude requirements, and a sustained rise in oil prices tends to widen the current account deficit, pressure the rupee, and squeeze margins for oil marketing companies, aviation stocks and other crude-sensitive sectors, all factors that traders are now weighing alongside the geopolitical risk itself.

Top Gainers & Losers 

Among the top gainers on the Nifty, ONGC (ONGC) rose 1.06% to an LTP of ₹241.01 from a previous close of ₹238.49, Mahindra & Mahindra (M&M) gained 0.86% to ₹3,419.40 against its previous close of ₹3,390.40, Maruti Suzuki (MARUTI) advanced 0.83% to ₹13,874 from ₹13,760, Eternal (ETERNAL) climbed 0.80% to ₹320.55 versus a previous close of ₹318, and Bajaj Auto (BAJAJ-AUTO) added 0.64% to trade at ₹11,738 against its previous close of ₹11,663.  

On the losing side, Infosys (INFY) declined 1.74% to ₹1,120.10 from a previous close of ₹1,139.90, Wipro (WIPRO) fell 1.46% to ₹179.25 against ₹181.90, Bharti Airtel (BHARTIARTL) slipped 1.38% to ₹1,942.10 from a previous close of ₹1,969.30, Tech Mahindra (TECHM) dropped 1.35% to ₹1,588.20 versus ₹1,610, and IndiGo (INDIGO) lost 1.22% to trade at ₹5,211 against its previous close of ₹5,275.50, with IT and telecom counters bearing the brunt of Tuesday’s selling. 

Broad Market & Sectoral Indices 

Among broad market indices, the Nifty Microcap 250 (up 0.31%), Nifty Smallcap 250 (up 0.14%) and Nifty Smallcap 100 (up 0.05%) were among the gainers, while the Nifty Midcap Select (down 0.35%), Nifty Midcap 100 (down 0.34%) and Nifty Midcap 50 (down 0.31%) led the decliners, pointing to relative resilience in smaller counters even as midcaps came under pressure. On the sectoral front, the Nifty Oil & Gas index (up 0.76%), Nifty Auto (up 0.66%) and Nifty Pharma (up 0.42%) were the top gainers, benefiting from the firmer crude backdrop and selective defensive buying, while the Nifty Realty index (down 1.41%), Nifty Capital Markets (down 1.18%) and Nifty IT (down 1.02%) were the biggest sectoral laggards, with IT continuing to weigh on the broader market for a second straight session. 

Middle East Conflict 

Iran said on Monday it would shift to a “fully offensive” military posture in the Strait of Hormuz after talks with the US to end the war stalled, with a senior Iranian official warning Tehran was prepared to launch a “timely and precise” attack to break the American naval blockade. The collapse comes as the June 17 memorandum of understanding, which had set a 60-day deadline for a broader peace deal, expired on Monday without renewal, after US President Trump confirmed Washington was not seeking an extension. Even as diplomatic back-channels reportedly continue between the Trump administration and Iran’s Revolutionary Guard Corps, Trump separately threatened to “bomb” Oman if it interfered with efforts to manage the strait, escalating tensions with a longstanding US Gulf ally. Thousands have already been killed in the conflict, and rising fuel costs tied to the war have become a growing domestic concern in the US ahead of November’s congressional elections. 

Asian Markets 

Asian markets were mixed on Tuesday morning, with Japan’s Nikkei 225 falling sharply by 1.62% to 68,098.54 and Hong Kong’s Hang Seng down 0.75%, while Indonesia’s Jakarta Composite bucked the trend to gain 1.59% and Thailand’s SET index rose 1.08%. The divergence reflected a broader split between markets more exposed to global risk sentiment and oil-price-sensitive trade flows, and those benefiting from domestic-led buying. 

US Markets 

US markets closed lower on Monday, with the Dow Jones Industrial Average falling 0.51% to 53,459.78 and the S&P 500 declining 0.52% to 7,745.06 as investors weighed the fallout from the collapsed Iran ceasefire and its impact on oil prices. The Nasdaq Composite and NYSE Composite also ended in the red, down 0.32% and 0.42% respectively, reflecting broad-based caution across Wall Street. 

Oil Prices 

Crude oil prices firmed up further in early trade on Tuesday, with WTI crude at $85.03 a barrel, up 0.63%, and Brent crude at $91.28, up 0.45%, continuing the upward move seen since the ceasefire’s collapse. Murban crude saw a particularly sharp jump of 9.26% to $97.70, reflecting acute regional supply concerns tied directly to the Strait of Hormuz standoff. With Brent having already touched a war-time peak of $126 a barrel, roughly 75% above pre-war levels, energy markets remain on edge over the risk of further disruption to tanker traffic through the strait. 

Indian Markets Close (Monday, August 17) 

Indian benchmark indices extended their cautious tone from last week on Monday, with the Sensex falling 281.09 points, or 0.36%, to close at 77,728.16, and the Nifty slipping 78.35 points, or 0.32%, to settle at 24,287.65, below the psychologically important 24,300 mark. Market breadth stayed weak through the session, with 2,213 shares declining against 2,025 advancing and 181 remaining unchanged on the NSE. IT stocks were the biggest drag, with the Nifty IT index falling nearly 2% as Infosys, HCL Technologies and TCS featured among the top Nifty losers alongside Sun Pharma and Nestle India. Metal stocks bucked the trend, with the Nifty Metal index rising 1.2% on the back of gains in Hindalco and Tata Steel, helping to cushion the broader market’s decline.

Sources

•  bseindia.com
• nseindia.com
• https://www.reuters.com/world/middle-east/iran-threatens-go-offensive-strait-hormuz-if-diplomacy-with-us-fails-2026-08-17/
• https://www.reuters.com/markets/stocks/americas/
• https://oilprice.com/oil-price-charts/